Anatomic risk of peroneal nerve injury with the "pie crust" technique for valgus release in total knee arthroplasty

Risk Factors for Peripheral Nerve Injury Following Revision Total Knee Arthroplasty in 132,960 Patients

BACKGROUND

Peripheral nerve injury (PNI) following revision total knee arthroplasty (rTKA) is a potentially devastating injury for patients. This study assessed the frequency of and risk factors for postoperative PNI following rTKA.

METHODS

Patients who underwent rTKA from 2003 to 2015 were identified using the National Inpatient Sample. Demographics, medical histories, surgical details, and complications were compared between patients who sustained a PNI and those who did not to identify risk factors for the development of PNI after rTKA.

RESULTS

Overall, 132,960 patients who underwent rTKA were identified, and 737 (0.56%) sustained a postoperative PNI. After adjusting for confounders, patients with a history of a spine condition (adjusted odds ratio [aOR]: 1.7, 95%-confidence interval 1.2 to 2.4, P = .003) and postoperative anemia (aOR: 1.3, 95%-CI: 1.1 to 1.5, P = .004) had higher risk of PNI following rTKA. Intraoperative periprosthetic fracture (aOR: 1.3, 0.78 to 2.2, P = .308), rheumatoid arthritis (aOR: 1.0, 95%-CI: 0.68 to 1.6, P = .865), and history of knee dislocation (aOR: 1.1, 95%-CI: 0.85 to 1.5, P = .412), were not significantly associated with higher risk for PNI.

CONCLUSIONS

This study found a 0.56% incidence of PNI following rTKA, and patients who had preexisting spine conditions or postoperative anemia were at an increased risk for this complication. Orthopedic surgeons may use the results of this study to appropriately counsel patients on the potential for a PNI following rTKA.

Influence and Clinical Significance of Knee Flexion Angle on the Anatomic Course of the Common Peroneal Nerve in the Posterolateral Corner of the Knee Joint

Background

Detailed knowledge of the anatomic course of the common peroneal nerve (CPN) is crucial for the surgical treatment of the posterolateral corner (PLC) of the knee.

Purpose

To investigate the relationship of the CPN to the PLC of the knee at different flexion angles.

Study Design

Descriptive laboratory study.

Methods

Ten healthy volunteers were recruited to undergo magnetic resonance imaging (MRI) of the knee joint at knee flexion angles of 0°, 30°, 60°, 90°, and 120°. MRI scans at 3 levels (joint line, tibial cut, and fibular tip) were evaluated to determine (1) the distance from the CPN to the PLC and (2) the distances between the CPN and the anterior-posterior and medial-lateral tibial axes. A 3-dimensional model of the knee joint created from MRI scans of a single participant was used to simulate the creation of a fibular tunnel for PLC reconstruction and investigate the relationship between the CPN, fibular tunnel, and guide pin.

Results

The CPN moved posteromedially with increased knee flexion angles. As the flexion angle increased, the distances from the CPN to the anterior-posterior axis and the PLC increased significantly, while the distance to the medial-lateral axis decreased significantly at all 3 measurement levels. The distances between the CPN and anterior-posterior and medial-lateral axes were significantly different among the different knee flexion angles at the different measurement levels. There were no significant differences in the mean distance from the CPN to the posterolateral border of the tibial plateau between 0° and 30° of flexion at the fibular tip level (P = .953). There were statistically significant differences in the distance from the CPN to the PLC of the tibial plateau at the different measurement levels. The 3-dimensional model demonstrated that the position of the CPN relative to the guide pin and the bone tunnel undergoes changes during knee flexion.

Conclusion

Changes in the knee flexion angle produced corresponding changes in the course of the CPN on the posterolateral aspect of the knee joint. The CPN moved posteromedially with increased knee flexion angles.

Clinical Relevance

Increasing the knee flexion angle during PLC reconstruction can effectively avoid direct injury of the CPN.

Total Knee Arthroplasty in the Valgus Knee

An estimated 10 to 15% of total knee arthroplasties (TKAs) are implanted for a diagnosis of arthritis when a valgus deformity is present. There are various techniques and considerations that must be considered for a successful TKA in a patient with a valgus deformity. This article provides a detailed summary of the anatomy, pathology, bone preparation, soft tissue management, implant selection, and complications when performing a TKA in a patient with valgus deformity.

Prophylactic Common Peroneal Nerve Decompression Avoids Nerve Palsy in Total Knee Arthroplasty for Severe Fixed Valgus Deformity: A Report of Four Cases and Review of Literature

Common peroneal nerve (CPN) injury is a serious complication following total knee arthroplasty (TKA). We aim to report four patients (five knees) who underwent prophylactic peroneal nerve decompression for severe rigid valgus deformity with or without associated fixed flexion deformity that was not correctable under anaesthesia. The preoperative deformity of 31.1° valgus by femorotibial angle (range 22.6-37.9°) improved to 7.1° valgus (range 4.3-9.1°) postoperatively (p < 0.05). For two knees, varus-valgus constrained was used due to medial laxity and the other three had posterior-stabilised prosthesis. All four patients had normal motor or sensory nerve function of the CPN nerve postoperatively. There was a significant improvement in the functional outcome by knee society score and knee society functional score from 17.8 ± 6.8, 25 ± 16.2 to 84 ± 8.7, 83 ± 10.3, respectively (p < 0.05). No complications were noted in the mean follow-up of 1.2 years. Prophylactic peroneal nerve decompression allows safe, adequate and optimal lateral soft-tissue release. It is effective in preventing common peroneal nerve palsy in high-risk patients like severe valgus and flexion deformity during total knee arthroplasty.

Minimum 2-Year Radiographic and Clinical Outcomes of Kinematic Alignment Total Knee Arthroplasty in the Valgus Knee

Kinematic alignment (KA) total knee arthroplasty (TKA) has gained popularity in the past decade, but outcomes of KA-TKA in the valgus knee have never been specifically evaluated. In this retrospective single institution study, we analyzed patient reported outcomes and radiographic measurements at minimum 2 years following KA-TKA for valgus knees (n = 51) and compared the results to KA-TKA performed for non-valgus knees (n = 275). The same approach, technique, and implants were used in both groups without the need to release soft tissues or use constrained implants. Surgery duration was similar between groups (p = 0.353). Lateral distal femoral angle was lower in the valgus group postoperatively (p = 0.036). In both groups significant improvement was seen in relieving pain and improving function, while average scores were superior in the non-valgus group for visual analog score (p = 0.005), oxford knee score (p = 0.013), and knee injury and osteoarthritis outcome score (p = 0.009). However, these differences did not translate to statistically significant differences in minimal clinical important difference achievement rates. In conclusion, KA-TKA is efficient in relieving pain and improving function, as reported in subjective questionnaires, and holds advantage in patients with valgus alignment by avoiding soft tissue releases and use of constrained implants. Future studies should examine whether bone loss occurs in the lateral distal femur.

Matched-Pair Analysis of Magnetic Resonance Images for Location of the Common Peroneal Nerve in Valgus Knees: Comparison with the Varus Knees

This study aimed to assess the distance and angular location of the common peroneal nerve (CPN) on axial magnetic resonance imaging (MRI) in the valgus knees and compare the measurements with those obtained from the control group. We compared the location of the CPN according to the type of alignment by performing a subgroup analysis. From January 2009 to December 2019, we identified 41 knees with preoperative MRI in patients who underwent total knee arthroplasty (TKA) for valgus deformity (valgus group). We performed one-to-two matched-pair analysis to a cohort of patients who underwent MRI but were not candidates for TKA (control group), according to sex and age. The valgus group was classified according to the grading system reported by Ranawat et al, and the control group was also subdivided according to the hip-knee-ankle (HKA) angle obtained from lower extremity scanography: neutral (-3 to +3 degrees from the neutral mechanical axis), valgus (> +3 degrees), and varus alignment (< -3 degrees). Distance between the CPN and posterolateral cortex of the tibia at the knee joint (distance J) and tibial cut level (distance C) were measured. Angle of the CPN from the central anteroposterior axis of the tibia (angle α) was measured. We compared the measurements between the groups. Distance J was significantly closer in the valgus group (p < 0.001), whereas angle α was significantly smaller in the valgus group (p < 0.001). However, no significant differences were found in the subgroup analysis. Moreover, a significant correlation was found between distance J and the HKA angle (p < 0.001). The location of the CPN in the valgus knees was closer to the posterolateral cortex of the tibia at the joint level and showed a smaller angle than that in the other aligned knees. We recommend that lateral soft tissue release for valgus knees should not be performed at the joint line. The results of this study suggest that this would be less safe than a release performed at the level of the proximal tibial bone resection.

Nerve Injuries in Total Knee Arthroplasty

Nerve injury is one of the potential complications of total knee arthroplasty. The extent of the injury includes motor and sensory dysfunction, either temporary or permanent. Although the consequences of nerve injury may be dramatic, the probability of occurrence during the course of primary knee arthroplasty is low, around 0.12% to 0.4%. Local dressing removal and knee flexion are imperative, and the initial investigations include ultrasound or MRI and nerve conduction studies. The extent of recovery depends on the type and severity of the initial nerve palsy; however, most patients are expected to have at least a partial recovery.

Management of instability after primary total knee arthroplasty: an evidence-based review

Background

Instability is one of the most common reasons for revision after a total knee replacement. It accounts for 17.4% of all single-stage revision procedures performed in the UK National Joint Registry. Through a careful patient evaluation, physical assessment and review of investigations one can identify the likely type of instability.

Aims

To critically examine the different types of instability, their presentation and evidence-based management options.

Method

A comprehensive literature search was conducted to identify articles relevant to the aetiology and management of instability in total knee replacements.

Results

Instability should be categorised as isolated or global and then, as flexion, mid-flexion, extension or recurvatum types. By identifying the aetiology of instability one can correctly restore balance and stability.

Conclusion

With careful judgement and meticulous surgical planning, instability can be addressed and revision surgery can provide patients with successful outcomes.

Magnetic resonance imaging evaluation of common peroneal nerve injury in acute and subacute posterolateral corner lesion: a retrospective study

Objective

To evaluate qualitative and quantitative magnetic resonance imaging (MRI) criteria for injury of the common peroneal nerve (CPN) in patients with acute or subacute injuries in the posterolateral corner (PLC) of the knee, as well as to evaluate the reproducibility of MRI evaluation of CPN alterations.

Materials and Methods

This was a retrospective study of 38 consecutive patients submitted to MRI and diagnosed with acute or subacute injury to the PLC of the knee (patient group) and 38 patients with normal MRI results (control group). Two musculoskeletal radiologists (designated radiologist A and radiologist B, respectively) evaluated the images. Nerve injury was classified as neurapraxia, axonotmesis, or neurotmesis. Signal strength was measured at the CPN, the tibial nerve (TN), and a superficial vein (SV). The CPN/TN and CPN/SV signal ratios were calculated. The status of each PLC structure, including the popliteal tendon, arcuate ligament, lateral collateral ligament, and biceps tendon, was classified as normal, partially torn, or completely torn, as was that of the cruciate ligaments. For the semiquantitative analysis of interobserver agreement, the kappa statistic was calculated, whereas a receiver operating characteristic (ROC) curve was used for the quantitative analysis.

Results

In the patient group, radiologist A found CPN abnormalities in 15 cases (39.4%)-neurapraxia in eight and axonotmesis in seven-whereas radiologist B found CPN abnormalities in 14 (36.8%)-neurapraxia in nine and axonotmesis in five. The kappa statistic showed excellent interobserver agreement. In the control group, the CPN/TN signal ratio ranged from 0.63 to 1.1 and the CPN/SV signal ratio ranged from 0.16 to 0.41, compared with 1.30-4.02 and 0.27-1.08, respectively, in the patient group. The ROC curve analysis demonstrated that the CPN/TN signal ratio at a cutoff value of 1.39 had high (93.3%) specificity for the identification of nerve damage, compared with 81.3% for the CPN/SV signal ratio at a cutoff value of 0.41.

Conclusion

CPN alterations are common in patients with PLC injury detected on MRI, and the level of interobserver agreement for such alterations was excellent. Calculating the CPN/TN and CPN/SV signal ratios may increase diagnostic confidence. We recommend systematic analysis of the CPN in cases of PLC injury.

Total knee arthroplasty in valgus knee deformity: is it still a challenge in 2021?

Total knee arthroplasty in valgus knee deformities continues to be a challenge for a surgeon. Approximately 10% of patients who undergo total knee arthroplasty have a valgus deformity. While performing total knee arthroplasty in a severe valgus knee, one should aware with the technical aspects of surgical exposure, bone cuts of the distal femur and proximal tibia, medial and lateral ligament balancing, flexion and extension gap balancing, creating an appropriate tibiofemoral joint line, balancing the patellofemoral joint, preserving peroneal nerve function, and selection of the implant regarding constraint. Restoration of neutral mechanical axis and correct ligament balance are important factors for stability and longevity of the prosthesis and for good functional outcome. Thus, our review aims to provide step by step comprehensive knowledge about different surgical techniques for the correction of severe valgus deformity in total knee arthroplasty.

Total Knee Arthroplasty with Concomitant Corrective Tibial Osteotomy Using Patient-Specific Instrumentation and Computed Tomography-Based Navigation in Severe Post-High Tibial Osteotomy Valgus Collapse

We report the case of a 78-year-old woman with lateral knee osteoarthritis and severe valgus knee deformity after high tibial osteotomy. The patient's severe valgus tibial deformity with a valgus angle of 45° was evaluated using a 3-dimensional bone model, and a closing-wedge osteotomy was planned. Combined total knee arthroplasty and closing-wedge tibial osteotomy were performed using patient-specific instrumentation and a computed tomography–based navigation system. A semiconstrained total knee system with a long stem was implanted for fixation of the osteotomy site in the tibia. The patient was able to walk without pain 2 years postoperatively. The Knee Society Score improved from 13 to 73 points, and the functional score improved from 30 to 65 points. This preoperative planning method and the treatment procedure would be beneficial for clinical decision-making and treatment of severe valgus knee deformities.

Total Knee Arthroplasty for Valgus Deformity via a Lateral Approach: Clinical Results, Comparison to Medial Approach, and Review of Recent Literature

BACKGROUND

Total knee arthroplasty (TKA) for valgus deformity is a challenge. The standard medial parapatellar approach may not be universally useful for this. We have adopted the lateral approach to valgus knees. Here we describe our experience with this approach, present early results, and compare them to the medial approach.

METHODS

Our institutional registry was queried for all patients with valgus deformity who underwent a TKA via a lateral approach between 2013 and 2016. The registry was also queried for patients with valgus deformity who underwent a TKA through a medial approach in previous years and this data was compared to the study group.

RESULTS

Seventy-nine valgus knees in 72 patients were operated through a lateral approach. Deformity was corrected by 10.8°, from 16.2° to 5.4° (P < .001). Patellar tilt improved from -2.3° to 0.3° (P = .037). Seven implants (9%) were constrained. Mean operating time was 87 minutes (range 53-137). Twenty-five knees in 23 patients were operated via the medial approach. Deformity was corrected by 7.3°, from 13.2° to 5.9° (P < .001). Mean operating time was 137 minutes (range 90-230). Constrained implants were used in 16% of cases. The lateral approach allowed better correction of valgus deformity (10.8 vs 7.3, P = .03) and shorter operative times (87 vs 137 minutes, P < .001).

CONCLUSION

A lateral approach TKA for valgus deformity improves knee alignment and patellar tilt. Compared to the medial approach, it allows better correction of the deformity, shorter operating times, and perhaps less use of constrained implants.

Common peroneal nerve 'pre-release' in total knee arthroplasty for severe valgus deformities

BACKGROUND

Common peroneal nerve (CPN) palsy is a devastating complication that follows total knee arthroplasty (TKA). However, there are only a few studies on concrete measures for protecting the CPN in patients. This study aimed to put forward the CPN 'pre-release' method to protect the nerve.

METHODS

A prospective study was conducted on 30 patients (34 knees) with severe valgus knees who underwent CPN pre-release. This was a two-incision approach, and required a separate dissection of about three centimeters from the TKA operation. Clinical measurements including pre- and postoperative motor and sensory nerve function of CPN, radiological evaluation, complications, and the revised data were analyzed and compared.

RESULTS

The average preoperative femorotibial angle was 31.3 ± 8.0°. All patients had completely normal motor (grade 5) and sensory nerve function of CPN postoperatively, and there was no transient or late-onset CPN palsy. Patients had a routine rehabilitation with full weight bearing after recovery from anesthesia, including the knees with unconstrained extension/flexion motion. During the last follow-up visit, the visual analog scale, Knee Society Score, Hospital for Special Surgery knee-rating scale, and range of motion were 2.06 ± 1.13, 92.18 ± 5.57, 90.18 ± 3.70, and 115.59 ± 7.76°, respectively. There were no revisions for instability and recurrent valgus deformities during follow-up. Also, the femorotibial angle, hip-knee-ankle angle, condylar-hip angle, and plateau-ankle angle were 4.9 ± 2.0°, 179.09 ± 3.21°, 89.97 ± 2.41°, and 90.53 ± 1.26°, respectively.

CONCLUSIONS

The CPN pre-release for severe valgus knees is an effective method for nerve protection, achieving an adequate and safe release of lateral soft tissue, and providing immediate and early functional rehabilitation with decreasing constrained implant.

Incidence and Risk Factors for Peripheral Nerve Injury After 383,000 Total Knee Arthroplasties Using a New York State Database (SPARCS)

BACKGROUND

Peripheral nerve injury (PNI) is a devastating complication following total knee arthroplasty (TKA). The purpose of this study is to identify risk factors for PNI after TKA using a New York Statewide Planning and Research Cooperative System.

METHODS

The Statewide Planning and Research Cooperative System database was queried to identify patients who had undergone TKA from 1996 to 2014. Patient demographics, medical history, surgical details, hospital characteristics, and in-hospital complications were recorded. Cases in which a new unilateral PNI was identified were compiled, as were control cases. The characteristics of cases and controls underwent univariate testing and a multivariate logistic regression using Akaike information criterion model selection to identify risk factors for the development of PNI after TKA.

RESULTS

In total, 383,060 cases were identified and 0.12%, or 445/383,060, experienced a new PNI. Pre-existing spinal conditions (odds ratio [OR] 1.98, confidence interval [CI] 1.08-3.30) and valgus deformity (OR 4.19, CI 2.46-6.66) were strongly correlated with the development of PNI postoperatively individually, but together increased risk substantially (OR 17.28, CI 2.83-55.35). Younger age (<50 years), in-hospital complications, female gender, and bilateral surgery were all associated with postoperative PNI, as well.

CONCLUSION

Valgus deformity and previous spine disorder together greatly increased the risk of PNI after TKA. Younger age, female gender, and in-hospital postoperative complications all increased the risk of PNI, as well. This study quantifies the relative risk each of these factors impart in the development of PNI after TKA and can help healthcare providers and systems identify and counsel patients at higher risk of this serious complication.

Step-wise medial collateral ligament needle puncturing in extension leads to a safe and predictable reduction in medial compartment pressure during TKA

PURPOSE

Medial soft tissue release in a varus deformity knee during total knee arthroplasty is essential for accurate balancing of the reconstruction. This study attempts to quantify the effect of sequential needle puncturing of the medial collateral ligament (MCL) using a pressure sensor insert (Verasense by OrthoSensor) and gap measurement under tension.

METHODS

Cruciate-retaining arthroplasties were placed in 14 cadaveric knees. The MCL was elongated by step-wise perforation, in five sets of five perforations, with the use of an 18-gauge needle, followed by valgus stress. Following the fifth set of needle perforations, blade perforation was performed on the remaining tense fibers of the MCL. Following each step-wise perforation, corresponding medial compartment pressures and gap measurements under tension were recorded.

RESULTS

Sensor measurements correlated closely with step-wise tissue release (R = 0.73, p < 0.0001), and a significant decrease in pressure was found in early needle puncturing (mean 49 N after 5, 83 N after 15, p values < 0.05), although changes diminished at later stages of needle perforation (90 N after 20). Gap measurement demonstrated small gradual changes with early puncturing, but showed significant opening in the later stages of release. There was minimal variation in pressure or gap measurements in flexion versus extension. This finding suggests that MCL needle puncture will not lead to unequal gaps between flexion and extension. There were no cases of MCL over-release after 15 punctures, one case after 20 punctures, and three after blade perforation.

CONCLUSION

Needle puncturing of the MCL in extension for up to 15 punctures can be a safe and predictable way to achieve medial opening when balancing a varus knee during TKA as demonstrated in this cadaveric model. Blade perforation should be used with caution to avoid over-release. The needle puncture method can be used by surgeons to achieve reliable reductions in medial compartment pressures, to help achieve a balanced TKA, with minimal risk of over-release.

Lateral Femoral Epicondylar Osteotomy for Correction of Fixed Valgus Deformity in Total Knee Arthroplasty: A Technical Note

BACKGROUND

Multiple surgical techniques exist to restore limb alignment and to balance soft tissues in valgus knees during total knee arthroplasty (TKA). One technique is to perform a lateral femoral epicondylar osteotomy.

METHODS

A retrospective analysis was performed on all patients with a fixed valgus deformity that was corrected with a lateral femoral epicondylar osteotomy during TKA. Preoperative and postoperative Knee Society Knee Scores, knee stability, range of motion, and radiographic alignment were recorded.

RESULTS

Ten patients (3 male and 7 female) underwent 12 TKAs by a single surgeon using a lateral femoral epicondylar osteotomy to correct a fixed valgus deformity. Implants used included 7 posterior stabilized, 3 constrained posterior stabilized, and 2 constrained condylar knees. Average age was 68 years (range 48-89) and average follow-up was 34.7 months (4-109). Average postoperative range of motion was 125° of flexion (range 95°-145°). The mean radiographic preoperative and postoperative anatomic tibiofemoral angles were 16.4° of valgus (range 12°-26°) and 5.5° of valgus (range 4°-7°), respectively. The mean preoperative knee society objective, satisfaction, expectation, and functional activity scores were 71, 20, 11, and 30, respectively. The mean postoperative knee society objective, satisfaction, expectation, and functional activity scores were 88, 34, 13, and 64, respectively. There was 1 postoperative deep vein thrombosis and 1 temporary peroneal nerve palsy.

CONCLUSION

Lateral femoral epicondylar osteotomy is a useful technique to restore mechanical alignment in fixed valgus deformities in TKA.

Location of the Common Peroneal Nerve in Valgus Knees-Is the Reported Safe Zone for Well-Aligned Knees Applicable?

BACKGROUND

Lateral soft-tissue release can jeopardize the common peroneal nerve (CPN) in total knee arthroplasty for valgus knees. Previous studies reporting safe zones to protect the CPN were based on well-aligned knees. We conducted this study to compare the localization of the CPN in well-aligned knees and in valgus knees.

METHODS

We conducted a consecutive 3-dimensional radiographic study on magnetic resonance images of 58 well-aligned knees and 39 valgus knees. We measured the distance between the CPN and the tibia, as well as the mediolateral, anteroposterior, and angular location of the CPN. We compared the results between well-aligned knees and valgus knees.

RESULTS

We found that there is an increased distance between the CPN and the tibia at the level of the tibial cut, but not at the joint line in valgus knees. It is safer to release the posterolateral capsule at the tibial side than at the level above this. The angular location and the mediolateral or anteroposterior location of the CPN in valgus knees are similar to those of well-aligned knees.

CONCLUSION

The location of the CPN in valgus knees is similar to that in well-aligned knees. The previously reported safe zone in well-aligned knees is applicable in valgus knees to protect the CPN.

Unconstrained total knee arthroplasty in significant valgus deformity: a modified surgical technique to balance the knee and avoid instability

PURPOSE

Correction of valgus deformity in total knee arthroplasty (TKA) is technically challenging and has produced variable results. A modified surgical technique involving adapting the distal femoral cut with minimal soft tissue release is proposed. The authors hypothesise that using this technique would result in satisfactory radiological and functional outcome.

METHODS

The technique involves balancing the knee in extension by changing the distal femoral resection angle and confining soft tissue release to only the posterolateral capsule if required. Retrospective analysis of 276 consecutive TKAs performed using this technique under the care of a single surgeon in patients with valgus knee deformity ≥10° was undertaken. An unconstrained mobile bearing implant was used in all knees with a medial para-patellar approach, and outcome scores were collected prospectively. Seventy-five percent of the knees were cementless. [corrected]

RESULTS

Mean coronal alignment of the lower limb was corrected from 15.6° (±5.7°) to 3.8° (±2.5°). 97.8 % knees had their coronal alignment restored to ≤7°. Seventy-eight knees (28 %) were balanced by only changing the distal femoral resection angle. One hundred and ninety-eight knees (72 %) had release of the posterolateral capsule. Sixteen knees (5.8 %) also had release of iliotibial band. Lateral patellar release was performed in 39 knees (14 %). 93.1 % had central patello-femoral alignment. At between 5.8 and 10.5 year follow-up, there has been one spinout, managed by closed reduction, and one revision of tibial tray for subsidence. The mean American Knee Society clinical score improved from 19.1 to 86.5 (±12.2).

CONCLUSION

Adequate correction of valgus knee deformity was successfully achieved using this modified technique with satisfactory medium-term outcome and avoidance of instability.

Clinical Outcomes of Patients with Valgus Deformity Undergoing Minimally Invasive Total Knee Arthroplasty Through the Medial Approach

Objective:

The purpose of this study was to compare the clinical outcomes between patients with a valgus or varus deformity undergoing minimally invasive total knee arthroplasty through the medial approach.

Methods:

The patients were classified into 2 groups according to the preoperative femorotibial angle measured on an anteroposterior long leg roentgenogram. The valgus group comprised of 26 knees in 21 patients with a femorotibial angle <170° (163.5 ± 5.7), and the varus group comprised of 24 knees in 21 patients with a femorotibial angle >190° (195.9 ± 5.5). The following background variables were compared between the groups: age at the time of the operation, sex, causative disease, preoperative femoral mechanical–anatomical angle, and postoperative knee range of motion, Knee Society score, femorotibial angle, and implant position.

Results:

There were significant differences between the valgus and varus groups in the age (68.0 ± 6.9 vs 75.8 ± 6.2 years), percentage of males (23.8% vs 0%), percentage with rheumatoid arthritis (61.9% vs 4.8%), and preoperative femoral mechanical–anatomical angle (6.2 ± 1.0° vs 7.4 ± 2.1°). Clinical outcome variables of postoperative femorotibial angle (173.1 ± 3.9° vs 175.2 ± 1.6°) and α angle (96.6 ± 3.1° vs 95.0 ± 1.9°) also differed.

Conclusion:

It was assumed that over-valgus resection of the femur is a contributory factor to residual valgus alignment. However, knee range of motion and Knee Society score did not differ between the groups. We suggest that minimally invasive total knee arthroplasty through the medial approach is one of the treatment options for patients with valgus deformity.

The Distance of the Common Peroneal Nerve to the Posterolateral Structures of the Knee

BACKGROUND

The common peroneal nerve (CPN) is an important structure of the lower limb and is at risk of injury during total knee arthroplasty. The aim of this study was to use a tibial reference system to determine the position of the CPN relative to the knee center and popliteus.

METHODS

Two hundred consecutive knee magnetic resonance images at the level of a standard tibial arthroplasty cut were evaluated for (1) distance of the CPN from the posterolateral capsule; (2) angle of the CPN from the center of the tibial anteroposterior axis; and (3) location of CPN with respect to the popliteus.

RESULTS

The mean distance between the CPN and the posterolateral joint capsule was 11.9 mm (range, 4.7-22.13 mm), which correlated positively with the medial-lateral axis of the tibia (Pearson correlation, 0.157; P = .026) and negatively with the angle of the nerve from the midline (Pearson correlation, -0.237, P = .001). The mean angle of the nerve from the midline was 42.2° (range, 25.0°-64.0°). In 116 knees (58%), the CPN was in line with the popliteus from the center of the knee, in 69 knees (34.5%) the CPN was lateral to the popliteus, and in 15 knees (7.5%), the CPN was medial to the popliteus. A danger zone was identified as between 29.95° and 54.57° from the anteroposterior axis.

CONCLUSION

The CPN is at risk during total knee arthroplasty. This study describes a method to help predict the location of the CPN intraoperatively and therefore avoid direct injury.

Medial collateral ligament lengthening by standardized pie-crusting technique: A cadaver study

INTRODUCTION

Pie-crusting (PC) is a tissue expansion technique using multiple perforation to lengthen the medial collateral ligament (MCL), but has still to be codified.

HYPOTHESIS

Standardized MCL PC allows measured opening of the medial femorotibial (MFT) joint line, without risk of MCL tear.

MATERIAL AND METHOD

Thirty-one knees were dissected, with medial parapatellar arthrotomy and resection of the cruciate ligaments and menisci. The deep MCL bundle was sectioned, and the thick anterior bundle (AB) of the MCL was observed in each knee. Knees were randomly allocated between AB sparing (AB+; n=15) or sectioning (AB-; n=16). A graduated dynometric tensor applied constant 80N distraction on the MFT joint line. MCL PC used a 19-G needle at the joint line, with a horizontal series of perforations every 2mm over the width of the MCL. MFT compartment opening was measured after each PC series.

RESULTS

Mean MFT space after sectioning the cruciate ligaments was 5.52±0.37mm, increasing by 1.64±1.28mm with AB sectioning. Twenty-five perforations were made in the AB+ and 16 in the AB- group. Final mean joint-line increase was 0.18±0.18mm in AB+ and 3.16±2.70mm in AB-. There were no MCL tears.

DISCUSSION

MCL pie-crusting was reliable and reproducible, achieving progressive MFT joint-line lengthening to a mean 8.71±2.62mm when associated to sectioning of the cruciate ligaments and MCL AB.

TYPE OF STUDY

Cadaver.

LEVEL OF EVIDENCE

IV.

Computed tomography evaluation in total knee arthroplasty: computer-assisted navigation versus conventional instrumentation in patients with advanced valgus arthritic knees

Arthritic knees with advanced valgus deformity present with soft tissue and osseous anomalies that make total knee arthroplasty (TKA) difficult. We conducted a retrospective chart review of 41 patients (51 knees) to determine whether computer-assisted surgery-TKA (CAS-TKA) is superior to TKA using conventional guiding systems. A significantly higher rate of lateral retinaculum release as well as outlier of sagittal mechanical axes and position of the femoral component (femoral flexion and femoral rotational angle) was recorded in the conventional TKA group versus the CAS-TKA group. Both groups had significant postoperative improvement in clinical performance, but results did not differ significantly between groups. Despite its radiographic benefit, CAS-TKA showed no significant benefit over TKA in short-term clinical functional outcomes when performed by an experienced surgeon.

The unstable knee

Instability after total knee replacement (TKR) accounts for 10% to 22% of revision procedures. All patients who present for evaluation of instability require a thorough history to be taken and physical examination, as well as appropriate imaging. Deep periprosthetic infection must be ruled out by laboratory testing and an aspiration of the knee must be carried out. The three main categories of instability include flexion instability, extension instability (symmetric and asymmetric), and genu recurvatum. Most recently, the aetiologies contributing to, and surgical manoeuvres required to correct, flexion instability have been elucidated. While implant design and patient-related factors may certainly contribute to the aetiology, surgical technique is also a significant factor in all forms of post-operative instability.

Cite this article: Bone Joint J 2014;96-B(11 Suppl A):112–4.

Preoperative templating and computer-assisted total knee arthroplasty for arthritic valgus knee

We reported the functional outcomes, component alignment and optimal thickness of the tibial inserts and joint line changes of 21 arthritic valgus knee deformities using preoperative templating and computer-assisted total knee arthroplasty(TKA). The osseous cut was modified using a novel preoperative templating technique. Soft tissue balance and component implantation were implemented with the aid of a computed tomography-free navigation system. The arthritic valgus knees had clinical, and functional improvement of the knee Society scores and Lysholm scores postoperatively, at an average of 37.8 ± 7.2 months. The mean anatomic axis (15.2° ± 4.5° vs. 6.1° ± 1.4°) and mechanical axis (8.3° ± 5.2° vs. 0.28° ± 1.6°) were also significantly improved postoperatively. The mean thickness of tibial inserts and joint line changes was 10.7 ± 1.46 mm and 0.1 ± 1.4 mm. This computer-assisted technique with preoperative radiographic templating is an alternative strategy to improve TKA results in arthritic valgus knees.

Anatomic proximity of the peroneal nerve to the posterolateral corner of the knee determined by MR imaging

BACKGROUND

The pie crusting technique has been extensively used to release the lateral soft tissue in total knee arthroplasty. However, it may place the peroneal nerve at direct injury risk when performed in a valgus knee. The aim of this study was to determine the anatomic proximity of the peroneal nerve to the posterolateral corner of the knee.

METHODS

One hundred knees were measured on axial MR images for the proximity of peroneal nerve to the closest edge of the inner surface of joint capsule or the posterolateral corner of proximal tibia at the level of the joint line and the level of the tibial cut respectively.

RESULTS

The distance between the peroneal nerve and the closest edge of the inner surface of joint capsule at the level of the joint line was 15.0 ± 2.6mm (range, 8.5-22.3mm), and the distance between the peroneal nerve and the posterolateral corner of proximal tibia was 14.0 ± 2.7 mm (range, 8.0-23.2mm). These distances were correlated with the anteroposterior diameter of the soft tissue of the knee, but not correlated with the size of the tibia.

CONCLUSIONS

These results suggest that it is safe enough providing that the scalpel blade does not pierce more than 8mm deep. However, patients with smaller legs are at greater risk of direct peroneal nerve injury.

Total knee arthroplasty in severe valgus knee deformity: comparison of a standard medial parapatellar approach combined with tibial tubercle osteotomy

PURPOSE

Primary TKA in valgus knees with a deformity of more than ten degrees may prove challenging, since bone and soft tissue abnormalities make accurate axis restoration, component orientation and joint stability attainment a difficult task. The purpose of this study was to determine which approach is optimal in these patients, by comparing the standard medial parapatellar approach to a lateral parapatellar combined with a tibial tubercle osteotomy (TTO).

METHODS

Forty-four valgus knees--with an axis deviation ranging from 15 to 36 degrees (mean 24°)--were dealt with primary TKA and followed up for a minimum period of 7 years. Lateral parapatellar arthrotomy combined with TTO was performed in 22 individuals (Group A) and a standard medial parapatellar capsulotomy in the remaining patients (Group B). The International Knee Society System Score (IKSS) was used for clinical evaluation. Radiological assessment was performed yearly postoperatively using long films for assessment of the anatomical axis.

RESULTS

The postoperative IKSS scores showed no significant statistical difference between groups A and B (P < 0.05). In the alignment parameter, however, residual valgus deviation occurred in 9% of patients from Group A and in 32% from Group B. No late-onset instability was displayed.

CONCLUSION

Lateral parapatellar approach combined with TTO may prove highly beneficial in significant valgus deformities, as the anatomical axis is restored accurately and soft tissue release of the lateral contracted structures facilitated to an important extent.

Total knee arthroplasty in severe valgus deformity: interest of combining a lateral approach with a tibial tubercle osteotomy

INTRODUCTION

Among the patients requiring total knee arthroplasty (TKA), approximately 10-15% presents with a valgus deformity (VD). Severely deformed valgus knees represent a surgical challenge. The purpose of this study is to evaluate the results of TKA in grade II and III valgus knee deformities (Ranawat classification), focusing on axis correction, by using a lateral parapatellar capsulotomy combined with tibial tubercle osteotomy.

HYPOTHESIS

The lateral approach in combination with a tibial tuberosity osteotomy is highly beneficial in the treatment of severe valgus knees in patients undergoing primary TKA, for correction of anatomical axis.

PATIENTS AND METHODS

Between January 1995 and December 2001, 33 patients with severe VD, grade II and III, were treated with TKA by one surgeon. Twenty-six patients (19 male, seven female) with mean age of 72 years (57-79) were dealt with a resurfacing posterior stabilized design; whereas in seven cases, a constrained type implant was used. These seven patients were excluded from the study. Two more patients were lost for follow-up and were also excluded. The axis deviation of the remaining 24 patients ranged from 15 to 35 degrees, (average 23°). A lateral parapatellar arthrotomy, in combination with tibial tubercle osteotomy was used. Patients' clinical evaluation - using the International Knee Society (IKS) score - with simultaneous radiological assessment was performed yearly after the operation; and for a mean follow-up time of 11.5 years (8 to 15 years).

RESULTS

The mean IKS score improved from 44 points (34 to 52) preoperatively, to 91 points (68 to 100) postoperatively, at the last follow-up. In terms of alignment parameter, only two knees had a residual valgus deviation greater than 7° (ideal range : 3-7°). One knee exhibited a 9° valgus, and another one 10°, according to anatomical axis measurments. In one case, there was a 5mm proximal migration of the osteotomised tuberosity fragment, due to breakage of the screw. However, the final outcome was not affected. There were no cases of tibial tubercle's non-union; neither of delayed instability.

CONCLUSION

The lateral approach is a useful approach in the treatment of severe valgus knee deformity in patients undergoing primary TKA. Anatomical axis restoration is facilitated, as the contracted structures are easily accessed and, in severe cases, the patellar alignment may be achieved by displacing the osteotomised tubercle. However, careful fixation of the tuberosity is mandatory.

LEVEL OF EVIDENCE

Level IV, prospective study of case series.

A new surgical technique for medial collateral ligament balancing: multiple needle puncturing

In this article, we present our experience with a new technique for medial soft tissue balancing, where we make multiple punctures in the medial collateral ligament (MCL) using a 19-gauge needle, to progressively stretch the MCL until a correct ligament balance is achieved. Ligament status was evaluated both before and after the procedure using computer navigation and mediolateral stress testing. The procedure was considered successful when 2 to 4-mm mediolateral joint line opening was obtained in extension and 2 to 6 mm in flexion. In 34 of 35 cases, a progressive correction of medial tightness was achieved according to the above described criteria. One case was considered overreleased in extension. Needle puncturing is a new, effective, and safe technique for progressive correction of MCL tightness in the varus knee.

The risk of direct peroneal nerve injury using the Ranawat "inside-out" lateral release technique in valgus total knee arthroplasty

The purposes of our study are to define a "danger zone" and a "safe zone" to avoid common peroneal nerve direct injury performing the "inside-out" release technique of posterior-lateral corner during total knee arthroplasty and to identify anatomic landmarks to localize the nerve before the soft-tissues release. Twenty cadaver dissections were used for testing. The distance from the nerve to the posterior-lateral corner of the tibia and to the posterior border of the iliotibial band averaged, respectively, 13.5 and 35.8 mm. The nerve is at risk during the release of the posterior-lateral capsule, in the triangle defined by the popliteus tendon, the tibial cut surface, and the most posterior fibers of iliotibial band (danger zone), but not during pie-crusting of the iliotibial band (safe zone).

Agreements between different methods of gap balance estimation in cruciate-retaining total knee arthroplasty

The authors investigated the agreements between three different methods of estimating gap balance in cruciate-retaining (CR) total knee arthroplasty (TKA) with the use of a subvastus approach. One hundred consecutive CR TKAs were prospectively included in this study. After completing soft tissue release and bone cutting for CR TKA, flexion-extension gap balance was assessed using a distractor, spacer blocks, and trial components. Levels of agreement between the estimation techniques used were substantial. All three techniques were reliable in the assessment of gap balance. But, observations made during this study suggest that if more than one estimation technique is applied during CR TKA, the incidence of undetected gap imbalance can be reduced.

Computer-assisted osteotomy of the lateral femoral condyle with non-constrained total knee replacement in severe valgus knees

We describe the mid-term results of a prospective study of total knee replacement in severe valgus knees using an osteotomy of the lateral femoral condyle and computer navigation. There were 15 knees with a mean valgus deformity of 21 degrees (17 degrees to 27 degrees) and a mean follow-up of 28 months (24 to 60). A cemented, non-constrained fixed bearing, posterior-cruciate-retaining knee prosthesis of the same design was used in all cases (Columbus-B. Braun; Aesculap, Tuttlingen, Germany). All the knees were corrected to a mean of 0.5 degrees of valgus (0 degrees to 2 degrees). Flexion of the knee had been limited to a mean of 85 degrees (75 degrees to 110 degrees) pre-operatively and improved to a mean of 105 degrees (90 degrees to 130 degrees) after operation. The mean Knee Society score improved from 37 (30 to 44) to 90 points (86 to 94). Osteotomy of the lateral femoral condyle combined with computer-assisted surgery gave an excellent mid-term outcome in patients undergoing total knee replacement in the presence of severe valgus deformity.

Total knee arthroplasty using a pie-crusting technique for valgus deformity

Valgus deformity correction with total knee arthroplasty is challenging. We hypothesized selective release of the tight lateral structures (pie-crusting technique), and of the lateral retinaculum in case of patellar maltracking, would obtain and maintain correction of the frontal plane deformity, restore patellar tracking and function, and avoid the complications of the extensive releases, including lateral condyle avascularity and residual lateral instability. We followed 48 patients with 53 valgus knees who underwent TKA and were followed a minimum of 5 years (mean, 8 years; range, 5-12 years). Soft tissue balancing of the lateral structures was performed with the pie-crusting technique. We employed either a fixed posterior stabilized or a mobile implant. A lateral release was performed in 67% of the cases. We observed one postoperative complication, a transient postoperative peroneal nerve palsy that spontaneously completely recovered. In 51 of the 53 knees (96%) we achieved alignment within 5 degrees from neutral. One patient had varus instability in extension. No component was revised. The pie-crusting technique reliably corrects moderate to severe fixed valgus deformities with a low complication rate and reasonable mid-term results. The multiple punctures allow gradual stretching of the lateral soft tissues and preservation of the popliteus tendon reducing the risk of posterolateral instability.

LEVEL OF EVIDENCE

Level IV, case series. See the Guidelines for Authors for a complete description of levels of evidence.

Clinical results in valgus total knee arthroplasty with the "pie crust" technique of lateral soft tissue releases

Numerous methods for creating symmetric flexion and extension gaps during knee arthroplasty in valgus knees have been proposed, and no consensus exists about the optimal technique. The "pie crust" technique for lateral soft tissue releases has been used extensively, yet few clinical results have been published. In this study, the clinical outcomes of 24 consecutive knees in 24 patients in whom this method was used in conjunction with a cemented posterior-stabilized prosthesis were evaluated. At a mean of 54 months' (range 24-69 months) follow-up, the knees were performing well with a mean Knee Society score of 97 (range 87-100) and mean range of motion of 121 degrees (range 100 degrees -145 degrees). Importantly, there were no clinical failures or cases of postoperative instability and no cases of radiographic loosening or wear.

Postarthroplasty ???Palsy??? and Systemic Neuropathy

Postarthroplasty palsy, occurrence of dysfunction of the sciatic or peroneal nerve after total joint replacement of the hip or knee, is a complication that remains poorly understood. Characteristics of a series of 24 patients with postarthroplasty palsy are reviewed, with the finding that, overall, 58.4% of the patients had an underlying peripheral neuropathy. The role of this neuropathy predisposing the arthroplasty patient to stretch/traction injury is discussed and should be emphasized as a risk factor prior to surgery and should influence the surgeon's intraoperative use of force during the arthroplasty procedure. This clinical problem is addressed from the perspective of peripheral nerve surgery, with an algorithm suggested for its management. The algorithm suggests that if a peroneal palsy is still present at 3 months after an arthroplasty and neurosensory testing fails to demonstrate a sensory reinnervation pattern in the territories of the deep or superficial peroneal nerve, then surgical neurolysis of the common peroneal nerve is indicated.

Missile-Caused Complete Lesions of the Peroneal Nerve and Peroneal Division of the Sciatic Nerve: Results of 157 Repairs

OBJECTIVE:

There are few large-volume studies of the repair of complete missile-caused peroneal nerve and peroneal division lesions. In this prospective study, the outcomes of such repairs are studied and the factors influencing the outcomes are analyzed.

METHODS:

During a 3-year period, 157 patients with complete missile-caused lesions of the peroneal nerve or peroneal division were treated surgically in the Belgrade Military Medical Academy: 37 patients with high-level (above the middle of the thigh), 90 patients with intermediate-level (above the popliteal crease), and 30 patients with low-level repairs. After at least 4 years of follow-up, outcome was defined on the basis of motor recovery, neurophysiological recovery, and patient judgment of the quality of outcome (poor, insufficient, good, or excellent). Good and excellent outcomes were considered successful. The factors of repair level, defect length, manner of repair, preoperative interval, severity of tissue damage in the repair region, and patient age were studied for their effect on outcome.

RESULTS:

A successful outcome was obtained in 10.8% of high-level repairs, 31.1% of intermediate-level repairs, and 56.7% of low-level repairs (P &lt; 0.001). Nerve defect and preoperative interval were significantly shorter for patients with a successful outcome compared with those with an unsuccessful outcome (P&lt; 0.001). Worsening of the outcome began with the nerve defect larger than 4 cm and preoperative interval greater than 3 months (P&lt; 0.001). Severity of local tissue damage significantly influenced the outcome (P= 0.008). Repair level (P&lt; 0.001), preoperative interval (P= 0.001), severity of local tissue damage (P= 0.011), and length of nerve defect (P= 0.011) were independent predictors for a successful outcome.

CONCLUSION:

After peroneal nerve or peroneal division repairs, a successful outcome is most probable with low-level lesions repaired in the first 3 months after injury using grafts smaller than 4 cm. Conversely, high-level repairs delayed for more than 7 months after injury and using grafts larger than 8 cm are probably not worthwhile.