Transcriptional time course after rotator cuff repair in 6 month old female rabbits

Introduction: Rotator cuff tears are prevalent in the population above the age of 60. The disease progression leads to muscle atrophy, fibrosis, and fatty infiltration, which is not improved upon with surgical repair, highlighting the need to better understand the underlying biology impairing more favorable outcomes. Methods: In this study, we collected supraspinatus muscle tissue from 6 month old female rabbits who had undergone unilateral tenotomy for 8 weeks at 1, 2, 4, or 8 weeks post-repair (n = 4/group). RNA sequencing and enrichment analyses were performed to identify a transcriptional timeline of rotator cuff muscle adaptations and related morphological sequelae. Results: There were differentially expressed (DE) genes at 1 (819 up/210 down), 2 (776/120), and 4 (63/27) weeks post-repair, with none at 8 week post-repair. Of the time points with DE genes, there were 1092 unique DE genes and 442 shared genes, highlighting that there are changing processes in the muscle at each time point. Broadly, 1-week post-repair differentially expressed genes were significantly enriched in pathways of metabolism and energetic activity, binding, and regulation. Many were also significantly enriched at 2 weeks, with the addition of NIF/NF-kappaB signaling, transcription in response to hypoxia, and mRNA stability alongside many additional pathways. There was also a shift in transcriptional activity at 4 weeks post-repair with significantly enriched pathways for lipids, hormones, apoptosis, and cytokine activity, despite an overall decrease in the number of differentially expressed genes. At 8 weeks post-repair there were no DE genes when compared to control. These transcriptional profiles were correlated with the histological findings of increased fat, degeneration, and fibrosis. Specifically, correlated gene sets were enriched for fatty acid metabolism, TGF-B-related, and other pathways. Discussion: This study identifies the timeline of transcriptional changes in muscle after RC repair, which by itself, does not induce a growth/regenerative response as desired. Instead, it is predominately related to metabolism/energetics changes at 1 week post-repair, unclear or asynchronous transcriptional diversity at 2 weeks post-repair, increased adipogenesis at 4 weeks post-repair, and a low transcriptional steady state or a dysregulated stress response at 8 weeks post-repair.

The “Second Hit” of Repair in a Rabbit Model of Chronic Rotator Cuff Tear

The rabbit supraspinatus is a useful translational model for rotator cuff (RC) repair because it recapitulates muscle atrophy and fat accumulation observed in humans after a chronic tear (the “first hit”). However, a timeline of RC tissue response after repair, especially with regard to recent evidence of muscle degeneration and lack of regeneration, is currently unavailable. Thus, the purpose of this study was to characterize the progression of muscle and fat changes over time after the repair of a chronic RC tear in the rabbit model. Two rounds of experiments were conducted in 2017–2018 and 2019–2020 with N = 18 and 16 skeletally mature New Zealand White rabbits, respectively. Animals underwent left supraspinatus tenotomy with repair 8 weeks later. The unoperated right shoulder served as control. The rabbits were sacrificed at 1-, 2-, 4-, and 8-weeks post-repair for histological and biochemical analysis. Atrophy, measured by fiber cross-sectional area and muscle mass, was greatest around 2 weeks after repair. Active muscle degeneration peaked at the same time, involving 8% of slide areas. There was no significant regeneration at any timepoint. Fat accumulation and fibrosis were significantly increased across all time points compared to contralateral. Statement of Clinical Significance: These results demonstrate model reproducibility and a “second hit” phenomenon of repair-induced muscle atrophy and degeneration which partially recovers after a short time, while increased fat and fibrosis persist.

Supraspinatus muscle architecture and physiology in a rabbit model of tenotomy and repair

Chronic rotator cuff tears can cause severe functional deficits. Addressing the chronic fatty and fibrotic muscle changes is of high clinical interest; however, the architectural and physiological consequences of chronic tear and repair are poorly characterized. We present a detailed architectural and physiological analysis of chronic tear and repair (both over 8 and 16 wk) compared with age-matched control rabbit supraspinatus (SSP) muscles. Using female New Zealand White Rabbits (n = 30, n = 6/group) under 2% isoflurane anesthesia, the SSP was surgically isolated and maximum isometric force was measured at four to six muscle lengths. Architectural analysis was performed, and maximum isometric stress was computed. Whole muscle length-tension curves were generated using architectural measurements to compare experimental physiology to theoretical predictions. Architectural measures are consistent with persistent radial and longitudinal atrophy over time in tenotomy that fails to recover after repair. Maximum isometric force was significantly decreased after 16 wk tenotomy and not significantly improved after repair. Peak isometric force reported here are greater than prior reports of rabbit SSP force after tenotomy. Peak stress was not significantly different between groups and consistent with prior literature of SSP stress. Muscle strain during contraction was significantly decreased after 8 wk of tenotomy and repair, indicating effects of tear and repair on muscle function. The experimental length-tension data were overlaid with predicted curves for each experimental group (generated from structural data), exposing the altered structure-function relationship for tenotomy and repair over time. Data presented here contribute to understanding the physiological implications of disease and repair in the rotator cuff.NEW & NOTEWORTHY We utilize an established method to measure the length-tension relationship for the rabbit supraspinatus in normal, torn, and repaired muscles. We then perform architectural analysis to evaluate structural changes after tear and repair. Although peak isometric force is lower in the tear and repair groups, there are no differences in peak stresses across groups. These findings indicate persistent structural changes (both radial and longitudinal atrophy) and physiological deficiencies (decreased peak force and uncoupling structure-function relationship) after tenotomy that do not significantly recover after repair.

Transcriptional Time Course After Rotator Cuff Tear

Rotator cuff (RC) tears are prevalent in the population above the age of 60. The disease progression leads to muscle atrophy, fibrosis, and fatty infiltration in the chronic state, which is not improved with intervention or surgical repair. This highlights the need to better understand the underlying dysfunction in muscle after RC tendon tear. Contemporary studies aimed at understanding muscle pathobiology after RC tear have considered transcriptional data in mice, rats and sheep models at 2–3 time points (1 to 16 weeks post injury). However, none of these studies observed a transition or resurgence of gene expression after the initial acute time points. In this study, we collected rabbit supraspinatus muscle tissue with high temporal resolution (1, 2, 4, 8, and 16 weeks) post-tenotomy (n = 6/group), to determine if unique, time-dependent transcriptional changes occur. RNA sequencing and analyses were performed to identify a transcriptional timeline of RC muscle changes and related morphological sequelae. At 1-week post-tenotomy, the greatest number of differentially expressed genes was observed (1,069 up/873 down) which decreases through 2 (170/133), 4 (86/41), and 8 weeks (16/18), followed by a resurgence and transition of expression at 16 weeks (1,421/293), a behavior which previously has not been captured or reported. Broadly, 1-week post-tenotomy is an acute time point with expected immune system responses, catabolism, and changes in energy metabolism, which continues into 2 weeks with less intensity and greater contribution from mitochondrial effects. Expression shifts at 4 weeks post-tenotomy to fatty acid oxidation, lipolysis, and general upregulation of adipogenesis related genes. The effects of previous weeks’ transcriptional dysfunction present themselves at 8 weeks post-tenotomy with enriched DNA damage binding, aggresome activity, extracellular matrix-receptor changes, and significant expression of genes known to induce apoptosis. At 16 weeks post-tenotomy, there is a range of enriched pathways including extracellular matrix constituent binding, mitophagy, neuronal activity, immune response, and more, highlighting the chaotic nature of this time point and possibility of a chronic classification. Transcriptional activity correlated significantly with histological changes and were enriched for biologically relevant pathways such as lipid metabolism. These data provide platform for understanding the biological mechanisms of chronic muscle degeneration after RC tears.

National Athletic Trainers' Association Position Statement: Management of Individuals With Patellofemoral Pain

OBJECTIVE: 

To present recommendations for athletic trainers and other health care providers regarding the identification of risk factors for and management of individuals with patellofemoral pain (PFP).

BACKGROUND: 

Patellofemoral pain is one of the most common knee diagnoses; however, this condition continues to be one of the most challenging to manage. Recent evidence has suggested that certain risk factors may contribute to the development of PFP. Early identification of risk factors may allow clinicians to develop and implement programs aimed at reducing the incidence of this condition. To date, clinicians have used various treatment strategies that have not necessarily benefitted all patients. Suboptimal outcomes may reflect the need to integrate clinical practice with scientific evidence to facilitate clinical decision making.

RECOMMENDATIONS: 

The recommendations are based on the best available evidence. They are intended to give athletic trainers and other health care professionals a framework for identifying risk factors for and managing patients with PFP.

Editorial Commentary: Got Evidence? What We Really Need Is an Algorithm for Treating Symptomatic Bipartite Patella

Bipartite patella is an uncommon but potentially troublesome problem for young athletes. Numerous uncontrolled retrospective studies have reported good results after various treatments. What is needed are studies that will guide workup and support treatment decisions based on the condition of the cartilage surfaces of the fragment, presence of pseudoarthrosis, and size and location of the fragment. To support decisions, we need prospective comparative studies, either randomized or, at least, prospective cohort studies that identify patients at the time of presentation, document key decision points, and follow patients to successful resolution of symptoms.

Effect of body mass index on patient outcomes of surgical intervention for the lumbar spine

BACKGROUND

Conflicting findings exist on the effect of obesity on outcomes of lumbar spine surgery; results depend on the diagnosis studied, procedure evaluated, definition of obesity, and specific outcomes measured. The purpose of this retrospective cohort study is to examine the effect of increasing body mass index (BMI) on surgical-related, health-related, and long-term outcomes of lumbar spine surgery in a single representative patient sample.

METHODS

Using a surgical registry from an integrated health care system, 8,049 instrumented lumbar spine cases were identified between 1/1/2009 and 09/30/2013. The sample was stratified into five BMI categories. Outcomes of interest included: (I) surgical-related factors and complications; (II) health-related complications; and (III) long-term complications. Mixed linear models, conditional logistic regressions, and survival analysis using a Cox regression model were conducted controlling for surgeon effects. Age, gender, diabetes status, smoking status, admitting diagnosis, and surgical approach were included as covariates.

RESULTS

Every 5 kg/m2 increase in BMI was associated with a significant increase in surgical time (7.8 minutes), estimated blood loss (EBL) (36.5 mL), risk of deep infection (OR =1.7 times), and deep vein thrombosis (DVT) (OR =1.5). BMI was not associated with increased incidence of other intraoperative or health-related complications. Rate of re-operation was 1.1 times higher with every 5 kg/m2 increase in BMI, but rate of re-operation due to adjacent segment disease (ASD) was not associated with BMI.

CONCLUSIONS

Obesity had an adverse effect on certain surgical-related, health-related and long-term surgical outcomes. The magnitude of this effect increased with increasing levels of obesity, which increases the medical burden associated with obesity.

A validated cadaveric model of trochlear dysplasia

PURPOSE

Despite the high prevalence of trochlear dysplasia among patients with patellar instability, it is not well studied and is infrequently addressed surgically. The lack of a validated cadaveric model of trochlear dysplasia may be a contributing factor. The goal of this study was to develop a simple, reproducible, and realistic cadaveric model of trochlear dysplasia by surgically modifying cadaveric femora with normal anatomy and then to validate this model through the use of mechanical and fluoroscopic measurements.

METHODS

The floor of the trochlear groove was surgically elevated using an inflatable bone tamp in eight cadaveric femora. The trochlear depth (TD) was measured with a custom-designed measuring device, and radiographic markers of dysplasia (sulcus angle, crossing sign, and prominence) were assessed before and after surgical modification.

RESULTS

The average TD was 3.6±1.4, 4.6±1.1, and 5.1±1.0 mm prior to reverse trochleoplasty (RT) and 1.0±1.8, 2.3±1.3, and 3.3±2.5 mm following RT at 0°, 20°, and 40° of flexion, respectively. These direct measurements of TD were confirmed with fluoroscopy. The sulcus angle averaged 141° prior to RT and 157° after RT. The average prominence across all specimens was 3.3±0.7 mm before RT, and 5.5±1.5 mm after RT. Finally, the crossing sign was found to be absent in all knees prior to RT and present in 7 of the 8 after RT.

CONCLUSIONS

The results of this study show that elevation of the trochlear floor with an inflatable bone tamp can reproducibly create a simulated dysplastic trochlea. This model may be useful in biomechanical studies of treatments for patellofemoral instability.

The risk of surgical site infection and re-admission in obese patients undergoing total joint replacement who lose weight before surgery and keep it off post-operatively

This study evaluated whether obese patients who lost weight before their total joint replacement and kept it off post-operatively were at lower risk of surgical site infection (SSI) and re-admission compared with those who remained the same weight. We reviewed 444 patients who underwent a total hip replacement and 937 with a total knee replacement who lost weight pre-operatively and sustained their weight loss after surgery. After adjustments, patients who lost weight before a total hip replacement and kept it off post-operatively had a 3.77 (95% confidence interval (CI) 1.59 to 8.95) greater likelihood of deep SSIs and those who lost weight before a total knee replacement had a 1.63 (95% CI 1.16 to 2.28) greater likelihood of re-admission compared with the reference group. These findings raise questions about the safety of weight management before total replacement of the hip and knee joints.

Medial patellofemoral ligament (MPFL) reconstruction for the treatment of patellofemoral instability

Patellofemoral instability can be a disabling problem. Numerous techniques are employed for its treatment. Medial patellofemoral ligament (MPFL) reconstruction in combination with other procedures has been explored by many orthopedic surgeons. The purpose of the study was to determine the effectiveness of isolated MPFL reconstruction in treating the symptoms associated with patellofemoral instability, preventing recurrence of patella dislocation, and returning patients to preinjury level of activity. This is a case series study. We conducted a clinical follow-up study on 56 knees (49 patients) after MPFL reconstruction for recurrent patellar instability with a mean follow-up of 4.3 years (range, 1.1-6.8). A single MPFL reconstruction technique was performed in all cases. Patient outcomes were evaluated using: International Knee Documentation Committee (IKDC) subjective knee form, Tegner activity score, functional hop test, and radiographs. Mean age at time of surgery was 24 years old (range, 13-49). Females comprised 75% of the sample. Mean interval from injury to surgery was 7.2 ± 8.6 years (range, 51 days-37 years). At follow-up, there were no recurrent dislocations reported, patella subluxation in 6 (11%) cases, and radiographic degenerative changes were none to mild in all patients. The series mean IKDC scores at follow-up was 76.3 ± 19.2 (range, 30-99), and Tegner activity scores were 5.6 ± 2.5. MPFL reconstruction is an option for treating the symptoms of patellar instability, preventing recurrent dislocation, and returning patients near to their preinjury level of activity. The level of evidence is IV.

The impact of pre-operative weight loss on incidence of surgical site infection and readmission rates after total joint arthroplasty

This study characterized a cohort of obese total hip arthroplasty (THA) and total knee arthroplasty (TKA) patients (1/1/2008-12/31/2010) and evaluated whether a clinically significant amount of pre-operative weight loss (5% decrease in body weight) is associated with a decreased risk of surgical site infections (SSI) and readmissions post-surgery. 10,718 TKAs and 4066 THAs were identified. During the one year pre-TKA 7.6% of patients gained weight, 12.4% lost weight, and 79.9% remained the same. In the one year pre-THA, 6.3% of patients gained weight, 18.0% lost weight, and 75.7% remained the same. In TKAs and THAs, after adjusting for covariates, the risk of SSI and readmission was not significantly different in the patients who gained or lost weight pre-operatively compared to those who remained the same.

Patellofemoral joint: from instability to arthritis

Disorders of the patellofemoral joint are commonly seen in musculoskeletal clinics. In recent years, the expansion of imaging techniques, improvements in correlative injury anatomy, and more focused physical examinations have resulted in new knowledge about patellofemoral disorders. To achieve optimal patient outcomes, it is helpful for orthopaedic surgeons who treat knee problems to review the management of patellar dislocations and isolated patellofemoral arthritis, including treatment algorithms.

A treatment algorithm for primary patellar dislocations

Context:

Primary patellar dislocation continues to be a common problem facing clinicians today. These injuries are associated with significant morbidity and a substantial recurrence rate. Myriad operative and nonoperative options have been described to treat these injuries, although the evidence-based literature is sparse.

Evidence Acquisition:

PubMed was searched from 1970-2010 to identify publications on patellar dislocations, including clinical presentation, natural history, radiographic workup, and treatment.

Results:

The initial workup of a patella dislocation includes a history, physical examination, and radiographs. If there is evidence of a displaced osteochondral fragment or hemarthrosis, then magnetic resonance imaging should be obtained. The treatment of first-time patella dislocators has been controversial, and no study has demonstrated a clear benefit to early operative intervention.

Conclusion:

First-time patellar dislocations should be treated conservatively unless there is evidence of a displaced osteochondral fragment.

Patient and surgeon characteristics associated with primary anterior cruciate ligament reconstruction graft selection

BACKGROUND

It has been suggested that a surgeon's experience and training are the most important factors associated with graft selection, but no studies have qualified this association. Graft usage prevalence has not been described for large anterior cruciate ligament reconstruction (ACLR) populations in the United States.

PURPOSE

To describe the prevalence of graft usage in a large community-based practice and evaluate the association of patient, surgeon, and site characteristics with choice of primary ACLR graft.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Primary ACLRs performed between February 2005 and June 2010 were selected for the study. A community-based ligament registry was used to identify cases and variables used for analysis. Graft choice (any allograft, hamstring autograft, and bone-patellar tendon-bone [BPTB] autograft) was compared by patient characteristics and surgeon and site characteristics. Associations between independent variables and graft choice were evaluated using a polychotomous regression model.

RESULTS

Of the 9849 patients included in the study, 64% were male, and overall median age was 28 years. Of these, 2796 (28.4%) received BPTB autografts, 3013 (30.6%) received hamstring autografts, and 4040 (41.0%) received allografts. The prevalence of graft source by patients' gender, race, age, body mass index (BMI), as well as surgeons' fellowship training status, average volume, and site volume were significantly different (all P < .001). Adjusted models showed that patients' gender (P < .001), race (P = .018), age (P < .001), BMI (P < .001), as well as surgeons' fellowship training status (P < .001), average volume (P < .001), and site volume (P < .001) are associated with graft selection. Older and female patients with lower BMI were more likely to receive allografts and hamstring autografts than BPTB autografts. Cases performed by non-fellowship-trained surgeons, lower volume sites, and/or lower volume surgeons were also more likely to be performed with allografts or hamstring autografts than BPTB autografts.

CONCLUSION

Gender, age, race, as well as facility and surgeon characteristics such as volume and location are associated with ACL graft choices.

Rehabilitation of the knee after medial patellofemoral ligament reconstruction

The principles of rehabilitation after medial patellofemoral ligament reconstruction are similar to those guiding rehabilitation after other ligamentous reconstructions of the knee, such as anterior cruciate ligament (ACL). The key features are to address pain control, range of motion (ROM), quadriceps strengthening, and proximal lower limb control. Return of full ROM, pain control, and protected weight bearing are stressed in the early phases of recovery. Progression of strength training and return to functional activities follow lines of evidence regarding graft necrosis, remodeling, and tunnel ingrowth, which are most commonly associated with ACL reconstruction.

Does discharge disposition after primary total joint arthroplasty affect readmission rates?

We reviewed 90-day readmission rates for 9150 patients with a primary total hip or knee arthroplasty performed between April 2001 and December 2004. Patients with an American Society of Anesthesiologists score of 3 or greater or with perioperative complications were excluded. We correlated the readmission rate with discharge disposition to either skilled nursing facilities (SNFs) or Home. Of the 9150 patients identified, 1447 were discharged to an SNF. After statistically adjusting for sex, age and American Society of Anesthesiologists scores, total hip arthroplasty and total knee arthroplasty patients discharged to SNFs had higher odds of hospital readmission within 90 days of surgery than those discharged home (total hip arthroplasty: odds ratio = 1.9; 95% confidence interval, 1.2-3.2; P = .008; total knee arthroplasty: odds ratio = 1.6; 95% confidence interval, 1.1-2.4; P = .01). Healthy patients discharged to SNFs after primary total joint arthroplasty need to be followed closely for complications.

Outcomes of routine use of antibiotic-loaded cement in primary total knee arthroplasty

The routine use of antibiotic-loaded bone cement (ALBC) in primary total knee arthroplasty (TKA) is controversial. Outcomes were recorded in patients who underwent primary TKA from May 2003 to March 2007 using a community-based total joint registry. Infection rates were compared in patients undergoing TKA with ALBC and regular cement. A total of 22 889 primary TKA were performed, with 2030 cases (8.9%) using ALBC. Two thousand four hundred forty-nine patients were diabetic (10.7%), with ALBC used in 295 cases (12%). The rate of deep infection was 1.4% for ALBC TKA (28 cases) and 0.7% (154 cases) with regular cement (P = .002). Among patients with diabetes, the infection rate was 1.7% (5 cases) with ALBC and 0.9% (19 cases) with regular cement (P = .199). In patients whom surgeons considered higher risk for infection, ALBC did not appear to reduce TKA infection rates. The routine use of antibiotic-laden cement warrants further investigation.

Knee replacement: epidemiology, outcomes, and trends in Southern California: 17,080 replacements from 1995 through 2004

BACKGROUND AND PURPOSE

There are limited population-based data on utilization, outcomes, and trends in total knee arthroplasty (TKA). The purpose of this study was to examine TKA utilization and short-term outcomes in a pre-paid health maintenance organization (HMO), and to determine whether rates and revision burden changed over time. We also studied whether this population is representative of the general population in California and in the United States.

METHODS

Using hospital utilization and membership databases from 1995 through 2004, we calculated incidence rates (IRs) of primary and revision TKA for every 10,000 health plan members. The demographics of the HMO population were compared to published census data from California and the United States.

RESULTS

The age and sex distributions of the study population were similar to those of the general population in California and the United States. 15,943 primary TKAs and 1,137 revision TKAs were performed during the 10-year period. Patients below the age of 65 accounted for one-third of all primary replacements and one-third of all revision replacements. IRs of primary TKAs increased from 6.3 per 10,000 in 1995 to 11.0 per 10,000 in 2004, at a rate of 5% per year (p<0.001). IRs of revision TKAs increased from 0.41 per 10,000 in 1995 to 0.74 per 10,000 in 2004 (p=0.4). Revision burden remained stable over the 10-year observation period. Surgical complications were higher in revision TKA than in primary TKA (10% vs. 7.7%; p=0.007). 90 day complication rates for primary and revision TKA including death were 0.3% and 0.6% (p=0.1) and for pulmonary embolism 0.5% and 0.4% (p=0.6). 90 day re-admission rates for primary and revision TKA including infection were 0.5% and 4.2% (p<0.001), for myocardial infarction 0.1% each, and for pneumonia 0.2% and 0.4% (p=0.08).

INTERPRETATION

The incidence of primary and revision TKA increased between 1995 and 2005. The rates of postoperative complications were low. Comparisons of the study population and the underlying general populations of interest indicate that this population can be used to predict the incidences and outcomes of TKA in the general population of California and of the United States as a whole.

The effect of ketorolac on anteroposterior knee laxity after anterior cruciate ligament reconstruction

This study investigated the effect of ketorolac on anteroposterior laxity after anterior cruciate ligament (ACL) reconstruction. A total of 168 ACL reconstructions performed between July 2003 and November 2004 were reviewed. The 6-week KT-1000 manual maximum differences between the ACL-reconstructed knee and nonoperative knee were compared for patients who received ketorolac and those who did not. Mean manual maximum difference in anterior displacement was 0.6 mm in the ketorolac group and -0.6 mm in the non-ketorolac group (P=.03). When bone-patellar tendon grafts were analyzed as a separate group, mean manual maximum difference was 0.5 mm in the ketorolac group and -1.4 mm in the non-ketorolac group (P=.007). When hamstring grafts were analyzed separately, mean manual maximum difference was 0.7 mm in the ketorolac group and 0.4 mm in the non-ketorolac group (P=.59). The use of ketorolac during bone-patellar tendon autograft ACL reconstruction was associated with increased AP laxity at 6 weeks postoperatively.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Biomechanical and anatomical assessment after knee hyperextension injury

BACKGROUND

Knee hyperextension can be a serious and disabling injury in both the athletic and general patient population. Understanding the pathoanatomy and pathomechanics is critical for accurate surgical soft tissue reconstructions.

PURPOSE

To quantify the effects of knee hyperextension injury on knee laxity in a human cadaveric model and to qualitatively assess the anatomical injury pattern through surgical dissection.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Six fresh-frozen cadaveric knees were rigidly mounted on a custom knee testing system that simulates clinical laxity tests. The knee laxity measurements consisted of anterior-posterior laxity, internal-external rotational laxity, and varus-valgus laxity using a custom testing setup and a Microscribe 3DLX system. The laxity data were collected at both 30 degrees and 90 degrees of knee flexion for the intact specimens and then after 15 degrees and 30 degrees hyperextension injury. After biomechanical assessment, a detailed dissection was performed to document the injured structures in the knee. Repeated-measures analysis of variance with a Tukey post hoc test (P < .05) was used for statistical comparison.

RESULTS

The results from this study suggest progressive damage to translational and rotational knee soft-tissue restraints with increasing knee hyperextension. Knee hyperextension to 30 degrees caused the most significant increase in anterior-posterior and rotational laxity. Anatomical dissections showed a general injury pattern to the posterolateral corner, partial femoral anterior cruciate ligament avulsion in 4 of 6 specimens, and no gross posterior cruciate ligament injuries.

CONCLUSION

Injuries to the posterolateral corner of the knee can result from isolated knee hyperextension.

CLINICAL RELEVANCE

The clinician should be aware of the potential for posterolateral corner injuries with isolated knee hyperextension. This will allow early surgical planning and primary surgical repair.

The kaiser permanente national total joint replacement registry

The Kaiser Permanente National Total Joint Replacement Registry (TJRR) is a national level database designed as a postmarket surveillance system for elective total hip and knee replacement. As of March 31, 2007, the TJRR recorded 16,945 primary total hip arthroplasties (THA), 2144 revisions (11.2%); and 30,815 total knee arthroplasties (TKA), 1794 revisions (5.5%). Statistically significant findings include: older age and higher American Society of Anesthesiology risk scores for revision THAs. Osteoarthritis is the most common diagnosis for THA and TKA, and aseptic loosening and instability are most common in revision THAs and TKAs. The TJRR has provided a mechanism for recalls, identified patients at risk for early revisions and changed practice by providing feedback to physicians.

Reliability of the international knee documentation committee radiographic grading system

BACKGROUND

The International Knee Documentation Committee (IKDC) forms are commonly used to measure outcomes after anterior cruciate ligament (ACL) reconstruction. The knee examination portion of the IKDC forms includes a radiographic grading system to grade degenerative changes. The interrater and intrarater reliability of this radiographic grading system remain unknown.

HYPOTHESIS

We hypothesize that the IKDC radiographic grading system will have acceptable interrater and intrarater reliability.

STUDY DESIGN

Case series (diagnosis); Level of evidence, 4.

METHODS

Radiographs of 205 ACL-reconstructed knees were obtained at 5-year follow-up. Specifically, weightbearing posteroanterior radiographs of the operative knee in 35 degrees to 45 degrees of flexion and a lateral radiograph in 30 degrees of flexion were used. The radiographs were independently graded by 2 sports medicine fellowship-trained orthopaedic surgeons using the IKDC 2000 standard instructions. One surgeon graded the same radiographs 6 months apart, blinded to patient and prior IKDC grades. The percentage agreement was calculated for each of the 5 knee compartments as defined by the IKDC. Interrater reliability was evaluated using the intraclass correlation coefficient (ICC) 2-way mixed effect model with absolute agreement. The Spearman rank-order correlation coefficient (r(s)) was applied to evaluate intrarater reliability.

RESULTS

The interrater agreement between the 2 surgeons was 59% for the medial joint space (ICC = 0.46; 95% confidence interval [CI] = 0.35-0.56), 54% for the lateral joint space (ICC = 0.45; 95% CI = 0.27-0.58), 49% for the patellofemoral joint (ICC = 0.40; 95% CI = 0.26-0.52), 63% for the anterior joint space (ICC = 0.20; 95% CI = 0.05-0.34), and 44% for the posterior joint space (ICC = 0.28; 95% CI = 0.15-0.40). The intrarater agreement was 83% for the medial joint space (r(s) = .77, P < .001), 86% for the lateral joint space (r(s) = .76, P < .001), 81% for the patellofemoral joint (r(s) = .79, P < .001), 91% for the anterior joint space (r(s) = .48, P < .001), and 69% for the posterior joint space (r(s) = .64, P < .001).

CONCLUSIONS

While intrarater reliability was acceptable, interrater reliability was poor. These findings suggest that multiple raters may score the same radiographs differently using the IKDC radiographic grading system. The use of a single rater to grade all radiographs when using the IKDC radiographic grading system maximizes reliability.

An Algorithm Guiding the Evaluation and Treatment of Acute Primary Patellar Dislocations

Primary patellar dislocation continues to be a common problem facing clinicians today. These injuries are associated with significant morbidity and a substantial recurrence rate. A myriad of operative and nonoperative options have been described to treat these injuries though the evidence-based literature is sparse. As a result, much controversy exists regarding the ideal management of the primary patellar dislocation. This article reviews the literature on this topic, from the initial examination and management to definitive treatment. Furthermore, an algorithm is presented to help the clinician approach and treat these patients.

Anatomical posterior cruciate ligament transplantation: a biomechanical analysis

BACKGROUND

Although current techniques of posterior cruciate ligament reconstruction may successfully stabilize the posterior cruciate ligament-deficient knee, no studies have demonstrated restoration of intact-knee kinematics.

HYPOTHESIS

Posterior cruciate ligament transplantation will successfully restore posterior stability and kinematics to the posterior cruciate ligament-deficient knee.

STUDY DESIGN

Controlled laboratory study.

METHODS

Seven pairs (donor/recipient) of size-matched cadaveric knees underwent a novel technique for posterior cruciate ligament transplantation. The grafts were fixed at the femoral origin and tibial insertion using an inlay technique with rigid fixation. The knees were tested in the intact (intact group), posterior cruciate ligament-deficient (deficient group), and posterior cruciate ligament-transplanted (transplant group) states. A 3-dimensional electromagnetic tracking system during an active knee extension and passive knee flexion maneuver was used to quantify kinematics, specifically looking at femoral rollback. KT ligament arthrometry was used to quantify posterior stability at the quadriceps neutral angle (70 degrees ).

RESULTS

For femoral rollback, the intact versus deficient groups was significantly different (P = .045) as was deficient versus transplant groups (P = .008) but not intact versus transplant groups. Similar differences were noted with the measurements of posterior stability (P < .001). Total posterior laxity between the intact versus deficient groups was significantly different (means, 1.32 mm vs 11.1 mm; P < .0001), as was deficient versus transplant groups (means, 11.1 mm vs 2.04 mm; P < .126) but not intact versus transplant groups.

CONCLUSION

In a posterior cruciate ligament-deficient cadaveric model, we demonstrated the technical feasibility and efficacy of posterior cruciate ligament transplantation for restoring femoral rollback and posterior stability at the quadriceps neutral angle.

CLINICAL RELEVANCE

Future studies in posterior cruciate ligament reconstruction should not only address stability but also restoration of normal knee kinematics in assessing the success of a given technique.

Rotator cuff muscle architecture: implications for glenohumeral stability

We examined the architectural properties of the rotator cuff muscles in 10 cadaveric specimens to understand their functional design. Based on our data and previously published joint angle-muscle excursion data, sarcomere length operating ranges were modeled through all permutations in 75 masculine medial and lateral rotation and 75 masculine abduction at the glenohumeral joint. Based on physiologic cross-sectional area, the subscapularis would have the greatest force-producing capacity, followed by the infraspinatus, supraspinatus, and teres minor. Based on fiber length, the supraspinatus would operate over the widest range of sarcomere lengths. The supraspinatus and infraspinatus had relatively long sarcomere lengths in the anatomic position, and were under relatively high passive tensions at rest, indicating they are responsible for glenohumeral resting stability. However, the subscapularis contributed passive tension at maximum abduction and lateral rotation, indicating it plays a critical role in glenohumeral stability in the position of apprehension. These data illustrate the exquisite coupling of muscle architecture and joint mechanics, which allows the rotator cuff to produce near maximal active tensions in the midrange and produce passive tensions in the various end-range positions. During surgery relatively small changes to rotator cuff muscle length may result in relatively large changes in shoulder function.

Complications of anterior cruciate ligament reconstruction

Injury to the anterior cruciate ligament (ACL) can result in recurrent instability, impairment, and progressive joint damage in athletes who return to high-risk sports activities. ACL reconstruction often is indicated. With refinement of surgical techniques and accelerated rehabilitation, the number of complications following ACL reconstruction has greatly decreased since the 1980s. Nevertheless, ACL reconstruction remains a complex procedure with multiple steps and many possible complications. Understanding the incidence and etiology of the more common complications associated with ACL reconstruction during the preoperative and postoperative periods is important to manage (if not avoid) the risk of these complications.

Obesity and perioperative morbidity in total hip and total knee arthroplasty patients

The incidence of obesity in 1071 total hip arthroplasty (THA) patients and 1813 total knee arthroplasty (TKA) patients and its effect on perioperative morbidity were evaluated prospectively. Fifty-two percent of TKA and 36% of THA patients were obese (body mass index >or=30). The obese patients were significantly younger, with a higher proportion of obese TKA patients being women. Higher rates of diabetes and hypertension were found in obese patients. Higher postoperative infection rates were observed in patients with body mass index 35 or higher. The odds ratio was 6.7 times higher risk for infection in obese TKA patients and 4.2 times higher for obese THA patients. The increased risk of infection in obese patients undergoing total joint arthroplasty must be realized by both the patient and surgeon.

Outcome instruments for patellofemoral arthroplasty

Although there are numerous patient outcome instruments available, the most reliable and valid instruments for evaluating patient outcomes after patellofemoral arthroplasty have not been identified. In this article, we review and evaluate the psychometric properties and practical considerations of administering general health instruments (Medical Outcomes Study (MOS) Short Form-36 and Short Form-12), knee scales (Knee Society Clinical Rating System, Knee Outcome Survey, International Knee Documentation Committee form, Knee Injury and Osteoarthritis Outcome Score) and a disease specific scale (Western Ontario and McMaster Universities Osteoarthritis Index) for patellofemoral arthroplasty outcome assessment. Based on our review of the literature, we recommend the Short Form-36 and Knee Injury and Osteoarthritis Outcome Score for evaluation of patellofemoral arthroplasty outcomes and provide recommendations for implementation of these instruments in a clinical setting.

Long-term results of lateral retinacular release

PURPOSE

We evaluated the outcomes of lateral retinacular release (LRR) after a long-term follow-up period of 5 to 12 years.

TYPE OF STUDY

Long-term retrospective clinical follow-up study.

PATIENTS AND METHODS

Between 1986 and 1994, 120 LRRs were performed in the Orthopaedic Department of the Catholic University of Rome. A total of 100 patients were evaluated. We divided the patients into 2 groups: group I contained 50 patients with patellar pain and no signs of instability; the remaining 50 patients, with clear signs of patellar instability, made up group II. Standard weight-bearing radiographs, axial views of the knee at 45 degrees , and dynamic computed tomography scans were performed in all patients preoperatively and at follow-up evaluation. Chondral damage was classified at the time of lateral release according to the criteria of Outerbridge and Dunlop. We used the Lysholm II score, which was modified for patellofemoral pathology and a clinical grading system of Busch and de Haven, to evaluate clinical outcomes at follow-up evaluation.

RESULTS

In group I (pain), 70% reported satisfactory outcomes at follow-up evaluation compared with 50% in group II (P < .05) (instability). Compared with a previously published analysis of 3-year outcomes in this same patient population, there was very little change in group I patients, whereas group II showed a significant decrease in good outcomes over time. The worst results were obtained in cases with serious cartilage damage and exposure of the subchondral bone at the time of lateral release.

CONCLUSIONS

LRR is a procedure offering a good percentage of success in the management of a stable patella with excessive lateral pressure and elective location of pain on the lateral retinaculum. In patellar instability the results are less favorable in long-term follow-up evaluation. The presence of high-grade joint surface injury is a poor prognostic indicator for lateral release.

LEVEL OF EVIDENCE

Level IV.

Posterolateral complex knee injuries: magnetic resonance imaging with surgical correlation

PURPOSE

To describe the magnetic resonance imaging (MRI) findings of injuries of the posterolateral aspect of the knee and to evaluate the diagnostic capabilities of MRI in the assessment of these injuries.

MATERIAL AND METHODS

The MRI studies of 14 patients (mean age 33 years) with trauma to the posterolateral aspect of the knee were retrospectively reviewed, and the imaging findings were correlated with those of surgery.

RESULTS

In all patients, MRI showed an intact iliotibial (ITB) band. MRI showed injury to the biceps tendon in 11 (79%), the gastrocnemius tendon in 1 (7%)), the popliteus tendon in 5 (36%), and the lateral collateral ligament (LCL) in 14 (100%) patients. Tear of the anterior cruciate ligament (ACL) was seen in 11 (79%) patients and tear of the posterior cruciate ligament (PCL) in 4 (29%) patients. With routine MRI, visualization of the popliteofibular or fabellofibular ligaments was incomplete. On MRI, the lateral meniscus and the medial meniscus were torn with equal frequency (n = 4; 29%). Osteochondral defects were seen in 5 (36%) cases and joint effusion in all 14 (100%) cases on MRI. Using surgical findings as the standard for diagnosis, MRI proved 86% accurate in the detection of injury to the ITB band, the biceps tendon (93%), the gastrocnemius tendon (100%), the popliteus tendon (86%), the LCL (100%), the ACL (79%), the PCL (86%), the lateral meniscus (90%), the medial meniscus (82%), and the osteochondral structures (79%). Surgical correlation confirmed the MRI findings of joint effusion in all cases.

CONCLUSION

MRI is well suited for demonstrating the presence and extent of injuries of the major structures of the posterolateral complex of the knee, allowing characterization of the severity of injury.

Prospective trial of a treatment algorithm for the management of the anterior cruciate ligament-injured knee

BACKGROUND

Specific guidelines for operative versus nonoperative management of anterior cruciate ligament injuries do not yet exist.

HYPOTHESIS

Surgical risk factors can be used to indicate whether reconstruction or conservative management is best for an individual patient.

STUDY DESIGN

Prospective nonrandomized controlled clinical trial; Level of evidence, 2.

METHODS

Patients were classified as high, moderate, or low risk using preinjury sports participation and knee laxity measurements. Early anterior cruciate ligament reconstruction (within 3 months of injury) was recommended to high-risk patients and conservative care to low-risk patients. It was recommended that moderate-risk patients have either early reconstruction or conservative care, according to the day of presentation. Assessment of subjective outcomes, activity, physical measurements, and radiographs was performed at mean follow-up of 6.6 years.

RESULTS

Early phase conservative management resulted in more late phase meniscus surgery than did early phase reconstruction at all risk levels (high risk, 25% vs 6.5%; moderate risk, 37% vs 7.7%, P = .01; low risk, 16% vs 0%). Early- and late-reconstruction patients' Tegner scores increased from presurgery to follow-up (P < .001) but did not return to preinjury levels. Early-reconstruction patients had higher rates of degenerative change on radiographs than did nonreconstruction patients (P < .05).

CONCLUSIONS

Early phase reconstruction reduced late phase knee laxity, risk of symptomatic instability, and the risk of late meniscus tear and surgery. Moderate- and high-risk patients had similar rates of late phase injury and surgery. Reconstruction did not prevent the appearance of late degenerative changes on radiographs. Relationship between bone contusion on initial magnetic resonance images and the finding of degenerative changes on follow-up radiographs were not detected. The treatment algorithm used in this study was effective in predicting risk of late phase knee surgery.

Variation in anterior cruciate ligament scar pattern: does the scar pattern affect anterior laxity in anterior cruciate ligament-deficient knees?

PURPOSE

This prospective study documented patterns of scar formation after anterior cruciate ligament (ACL) rupture in order to test the hypothesis that ACL remnants can contribute to anterior knee passive motion limits tested with a ligament arthrometer.

TYPE OF STUDY

Prospective cohort study.

METHODS

Forty-eight consecutive patients undergoing ACL reconstructions had intra-operative ligament arthrometry testing before and immediately after preparation of the notch and debridement of the ACL remnant. Patterns of scar formation were compared with changes in knee laxity after debridement of the ACL remnant.

RESULTS

Eighteen patients (38%) had ligament scarring to the posterior cruciate ligament (group 1). Four patients (8%) had scar tissue that appeared to extend from the ACL fibers to the roof of the notch (group 2). Six ACL remnants (12%) appeared to have healed to the lateral wall of the notch or the medial aspect of the lateral femoral condyle in a position anterior and distal to the ACL anatomic footprint (group 3). In 20 patients (42%), there was no identifiable ligament tissue remaining (group 4). Changes in anterior laxity were associated with the specific pattern of scar formation within the notch. The greatest increase in anterior laxity after debridement was observed in knees in which the injured ACL had an aberrant reattachment to the femur: group 1 (mean, -1.3 mm; P < .01), group 2 (mean, -3.4 mm; P < .05), and group 3 (mean, -4.3 mm; P < .05). In group 4, the change in knee laxity was not significant (mean, 0.2 mm; 95% CI, -0.29 to 0.74 mm). Overall, 14 of 48 knees (29%) loosened more than 2 mm after ACL resection ( P < .01).

CONCLUSIONS

Resection of the ACL scar resulted in a measurable increase in passive anterior laxity in a subset of ACL-deficient knees. This increase in anterior laxity occurred in patients whose ligament healed to the femur, effectively crossing the joint. When performing arthroscopy without reconstruction in ACL-injured knees, we recommend caution in resecting the torn ACL or scar tissue because removal of this tissue contributed to increased anterior laxity in some ACL-deficient knees.

LEVEL OF EVIDENCE

Level II, diagnostic study of consecutive patients.

Epidemiology and natural history of acute patellar dislocation

BACKGROUND

The goals of this study were to (1) define the epidemiology of acute patellar dislocation, (2) determine the risk of subsequent patellar instability episodes (subluxation and/or redislocation) during the study period, and (3) identify risk factors for subsequent instability episodes.

STUDY DESIGN

Prospective cohort study.

METHODS

The authors prospectively followed 189 patients for a period of 2 to 5 years. Historical data, injury mechanisms, and physical and radiographic measurements were recorded to identify potential risk factors for poor outcomes.

RESULTS

Risk was highest among females 10 to 17 years old. Patients presenting with a prior history of instability were more likely to be female (P < .05) and were older than first-time dislocation patients (P < .05). Fewer first-time dislocators (17%) had episodes of instability during follow-up than patients with a previous history of instability (49%) (P < .01). After adjusting for demographics, patients with a prior history had 7 times higher odds of subsequent instability episodes during follow-up than first time dislocators (adjusted odds ratio = 6.6, P < .001).

CONCLUSIONS

Patellar dislocators who present with a history of patellofemoral instability are more likely to be female, are older, and have greater risk of subsequent patellar instability episodes than first-time patellar dislocators. Risk of recurrent patellar instability episodes in either knee is much higher in this group than in first-time dislocators.

Lateral retinacular release: a survey of the International Patellofemoral Study Group

PURPOSE

The purpose of this investigation was to determine current views regarding lateral release among experienced knee surgeons with a specific interest in the patellofemoral joint.

TYPE OF STUDY

Scientific survey.

METHODS

A questionnaire was developed and mailed to all members of an international group with a specific interest in disorders of the patellofemoral joint. Frequencies and percentages of responses were calculated for each question to determine surgeon consensus. We measured agreement among responses using the kappa statistic. This provided an indication of consistency for each question as well as correlation among the responses to different questions.

RESULTS

The survey response rate was 60%. Isolated lateral release was estimated to account for only 1 to 5 surgical cases per respondent per year, or 2% of cases performed annually. In the setting of arthroscopy or exploration, 74% of respondents believed that lateral release calls for specific informed consent. Strong consensus was found that objective evidence is needed to justify lateral release, but agreement was poor as to what clinical evidence provides the most appropriate indication for the procedure.

CONCLUSIONS

Even among experienced knee surgeons with a special interest in diseases of the patellofemoral articulation, isolated lateral release is rarely performed. Strong consensus was found that isolated lateral release should not be undertaken without prior planning in the form of objective clinical indications and preoperative informed consent.

LEVEL OF EVIDENCE

Level V.

Indications in the treatment of patellar instability

Recent developments in patellar instability have focused on the passive restraints against mediolateral patellar motion. Viewed from this perspective, muscle alignment is considered secondary because, although muscle forces are important, their ability to cause or prevent patellar dislocation depends on passive stability or the lack thereof. In the normal knee, the patella seats quickly in the trochlea in early flexion, so that the ligamentous restraints are important only near full extension. In the unstable patellofemoral joint, the trochlea frequently is deficient and patella alta often exists. In such cases, the ligaments assume a greater role in preventing excessive lateral patellar displacement. The most pressing questions at the moment are: 1) which of the anatomical abnormalities must be corrected, alone or in combination, to prevent further patellar instability; and 2) what is the relative risk of corrective procedures compared to the natural history or competing surgical approaches? These questions must be addressed by clinical trials. Only a minority of patients who experience patellar dislocation will redislocate the patella, and surgical treatment does not always yield results that are superior to conservative care. Treatment recommendations should be based on an individual's risk of recurrent dislocation, pain, and disability, a thorough understanding of his or her anatomy, and clear treatment objectives. Lateral release has no role in the treatment of a hyperlax patellofemoral joint, as it adds additional laxity to a system that is already unstable. If surgery is performed, current evidence suggests techniques aimed at repair or reconstruction of the passive retinacular restraints are as effective as more extensive procedures at preventing subsequent dislocations. Among the latter procedures, realignment procedures use active muscle forces to help seat the patella in the femoral groove; however, biomechanical costs are associated with this approach and superior results have not been demonstrated with distal and combined realignments compared with more limited proximal procedures.

The reliability and validity of knee-specific and general health instruments in assessing acute patellar dislocation outcomes

BACKGROUND

The most reliable and valid instruments for assessing patient outcome after patellar dislocation have not been identified.

HYPOTHESIS

Knee-specific and general health instruments will differ in validity and reliability for patients with patellar dislocation.

STUDY DESIGN

Prospective cohort study.

METHODS

Subjects consisted of 153 patients with acute patellar dislocation (110 with first-time dislocations and 43 with a history of patellofemoral subluxation or dislocation). We administered the modified International Knee Documentation Committee form, Kujala, Fulkerson, Lysholm, Tegner, Short Form 36, and Musculoskeletal Function Assessment instruments on two separate occasions (test-retest reliability). Validity was assessed by comparing scores of the two groups and by comparing scores of patients with and without recurrent subluxations/dislocations during follow-up.

RESULTS

The knee-specific instruments yielded the highest test-retest reliability. The knee-specific and general health instruments identified higher disability levels in the patients with a history of patellofemoral problems than in those with first-time dislocations. The general health instruments identified higher disability levels in patients with patellar dislocation than published norms. The Fulkerson and Lysholm scales were the only instruments to differentiate between patients with and without recurrent subluxations/dislocations.

CONCLUSIONS

Knee-specific scales yielded higher reliability coefficients and stronger validity than did general health instruments. Knee-specific, general health, and activity level instruments are complementary and in combination provide a more complete assessment for patients with patellar dislocation.

Acute lateral patellar dislocation at MR imaging: injury patterns of medial patellar soft-tissue restraints and osteochondral injuries of the inferomedial patella

PURPOSE

To assess magnetic resonance (MR) imaging findings after acute lateral patellar dislocation (LPD) with emphasis on the medial patella restraints and to describe a medial patellar impaction deformity.

MATERIALS AND METHODS

Knee MR images obtained within 8 weeks after LPD were evaluated for medial retinacular and medial patellofemoral ligament (MPFL) disruption, vastus medialis obliquus (VMO) edema and/or elevation, and other derangements. One hundred patients with no evidence of prior LPD were evaluated as controls. The Student t test was used for statistical comparisons.

RESULTS

Eighty-two examinations were performed in 81 patients with LPD (mean age, 20 years; age range, 9-57 years). Seventy-six percent (62 of 82 examinations) showed medial retinacular disruption at its patellar insertion; 30% (25 of 82), at its midsubstance. The MPFL femoral origin was identified in 87% (71 of 82); of these, 49% (35 of 71) showed injury. Forty-eight percent (39 of 82) showed more than one site of injury to the medial stabilizers; 45% (37 of 82) showed edema or hemorrhage at the inferior VMO. Mean VMO elevation in the coronal plane of the adductor tendon was 2.2 cm, with a range of 0.6-4.5 cm (in control subjects, 0.9 cm; range, 0.1-2.5 cm; P <.001). At the inferomedial patella, 70% (57 of 82) of LPD examinations showed osteochondral injury and 44% (36 of 82) showed concave impaction deformity (0 of 100 control subjects). Other examination findings in LPDs included contusions of the lateral femoral condyle (66 [80%] of 82 examinations) or medial patella (50 [61%] of 82), intraarticular bodies (12 [15%] of 82), effusion (45 [55%] of 82), medial collateral injury (nine [11%] of 82), and meniscal tear (nine [11%] of 82).

CONCLUSION

Injury to the medial retinaculum, MPFL, and VMO may be identified at MR imaging after acute LPD. Concave impaction deformity of the inferomedial patella is a specific sign of prior LPD.

Fate of the anterior cruciate ligament-injured knee

Most patients with anterior cruciate ligament (ACL) injuries do well with activities of daily living even after follow-up in the range of 5 to 15 years. Most can participate in some sports activity if they are inclined to do so, but most will have some limitations in vigorous sports, and only a few will be entirely asymptomatic. The challenge to the clinician is to understand and predict how ACL deficiency in a given patient will affect that patients's life and activities. In counseling patients about treatment after an ACL injury, the clinician can use knee ligament arthrometry measurements and pre-injury sports activity to estimate the risk of injury over the next 5 to 10 years. Meniscus, chondral, and sub-chondral injuries are not uncommon, but rarely require surgical intervention in the early phase of ACL deficiency. The prevalence of clinically significant meniscal damage increases with time, and is associated with increasing disability, surgery, and arthrosis in high-risk patients. Ligament reconstruction has not been shown to prevent arthrosis, but in prospective studies it appears to reduce the risk of subsequent meniscal injury, improve passive anteroposterior knee motion limits, and facilitate return to high-level sporting activities.

Techniques of medial retinacular repair and reconstruction

Insufficiency of the passive patellar restraints results in lateral patellar instability by allowing excessive lateral displacement of the patella. Although the surgical approach to patellar instability traditionally has been to realign the dynamic elements (muscle forces) that pull the patella laterally, newer techniques have sought to restore the integrity of key medial passive (ligamentous) stabilizers. An increasing body of evidence indicates that the chief medial ligamentous restraint is the medial patellofemoral ligament. The current authors examine the principles of medial retinacular repair and reconstruction as they relate to patellar stability. Individual techniques and approaches are discussed, including primary repair with or without augmentation, and reconstruction using autogenous tendon, allografts, and synthetic graft materials. These procedures share the common objective of addressing the essential lesion in lateral patellar instability to restore the normal passive restraints against lateral patellar displacement.

Current concepts of lateral patella dislocation

Surgical treatment of patellar dislocations, acute and chronic, has evolved significantly over the past decade with the advance of biomechanical knowledge of patellofemoral restraints and injury patterns identified by physical examination and improved imaging techniques. There continues to be no consensus on treatment parameters. Despite the presence of predisposing factors, such as dysplasia or generalized hyperlaxity, medial retinacular injury associated with primary (first-time) patellar dislocations represents a ligament injury, which may result in residual laxity of the injured structure. This residual laxity is defined objectively by an increase in passive lateral excursion of the patella. Repair or reconstructive procedures to restore this medial constraint is considered paramount in any procedure to stabilize the patella against subsequent dislocations. How best to accomplish this continues to be a matter of debate. The establishment of a medial check-rein by either repairing or reconstructing the MPFL is the procedure of choice for stabilizing a kneecap after first-time dislocation, largely because the literature to date does not provide clear guidelines about when more extensive surgery is indicated. Whether or not all first-time dislocators have improved outcome after surgical repair remains speculative, however. Improved outcome would involve both the elimination of recurrent instability episodes and continued satisfactory function of this patella in activities-of-daily-living and sporting activities. These outcomes have not been studied critically in operative versus nonoperative treatment of first-time patellar dislocation. For the first-time dislocator, most investigators would agree that an arthroscopy should be performed if intra-articular chondral damage is suspected. Nonoperative management of first-time patellar dislocations continues to be the preferred practice pattern in the United States. If surgical management is elected, because of individual characteristics of the injury pattern or the patient's lifestyle, it is important to inspect the MPFL along its length and repair any or all ligamentous disruptions. If the ligament is avulsed from the medial epicondyle, reattachment to bone is necessary to restore passive restraint to lateral patella motion. MRI may be useful in order to identify the location and degree of medial soft tissue injury preoperatively. The establishment of a medial check-rein by either repairing or reconstructing the MPFL is a necessary component of all surgical procedures performed to correct objective lateral instability of the patella. The addition of a LRR should be additive to this procedure only when it facilitates other procedures to recenter the patella or when objective lateral tilt by physical examination measurements is present. A practical approach to surgery after patellar dislocation is the minimal amount of surgery necessary to re-establish objective constraints of the patella. Correcting dysplastic factors, in particular tibial tubercle transfers and trochleoplasties, are best reserved if more minimal surgery has failed. This failure is defined as continued functional instability of the kneecap.

Characteristics of patients with primary acute lateral patellar dislocation and their recovery within the first 6 months of injury

We prospectively studied the characteristics and early recovery of an unselected population of patients who had acute first-time lateral patellar dislocation. The recovery program used standardized rehabilitation, emphasizing range of motion, muscle strength, and return of function. Patients returned to stressful activities including sports as tolerated when they regained full passive range of motion, had no effusion, and when quadriceps muscle strength was at least 80% compared with the noninjured limb. Seventy-four patients met the enrollment criteria; 37 men and 37 women. The average age was 19.9 years, and preinjury sports participation was similar to that of ligament-injury patients. Four percent of patients (N = 3) had a history of birth complications, 3% (N = 2) had a history of lower extremity problems as an infant or child, and 9% (N = 7) had a family history of patellar dislocation. Radiographs revealed a 50% incidence (N = 37) of patella alta; all patients demonstrated lateral patellar overhang. Patients regained range of motion (mean, 0 degrees to 132 degrees) by 6 weeks. Sports participation remained significantly reduced throughout the first 6 months after injury, with the greatest limitations in kneeling and squatting. At 6 months, 58% of patients (N = 43) noted limitation in strenuous activities. The patients who had acute primary patellar dislocation were young and active. Most injuries occurred during sports, and few patients had abnormal physical features, contradicting any stereotype of an overweight, sedentary, adolescent girl whose patella dislocates with little or no trauma.

Medial soft tissue restraints in lateral patellar instability and repair

This study was undertaken to evaluate the medial ligamentous stabilizers of the patella in restraining lateral displacement and to assess their relative contribution after individual repair. Seventeen fresh frozen human anatomic specimen knee joints were studied. The specimens were loaded onto a testing instrument that was designed to measure the compliance of the medial and lateral patellar restraints in the coronal plane. Two different cutting and repair sequences were used to test the individual contributions of the patellar ligaments. The medial patellofemoral ligament was found to be the major medial ligamentous stabilizer of the patella. Isolated release resulted in a 50% increase in lateral displacement, and isolated repair restored balance to the patella. In addition, the patellotibial and patellomeniscal ligament complex played an important secondary role in restraining lateral patellar displacement. Isolated repair of these ligaments restored balance to near normal levels. The medial patellofemoral retinaculum played only a minor role in patellofemoral instability. Proximal realignment or medial ligament repair for patellofemoral instability specifically should address repair of the deep layers that contain the restraints to lateral patellar displacement. Failure to include these structures in repair, especially of the medial patellofemoral ligament, may lead to persistent or recurrent instability.