Modified pre-curved patellar basket plate, reconstruction of the proper length and position of the patellar ligament--a biomechanical analysis

Anterior variable-angle locked plating versus tension band wiring of simple and complex patella fractures - a biomechanical investigation

BACKGROUND

The aim of this study was to investigate the biomechanical performance of novel anterior variable-angle locking plates versus tension band wiring used for fixation of simple and complex patella fractures.

METHODS

Sixteen pairs of human cadaveric knees were used to simulate two-part simple transverse AO/OTA 34-C1 and five-part complex AO/OTA 34-C3 patella fractures. The complex fracture pattern was characterized with a medial and a lateral proximal fragment, together with an inferomedial, an inferolateral and an inferior fragment mimicking comminution around the distal patella pole. Eight pairs with simple fractures were split for fixation via either tension band wiring (TBW) through two parallel cannulated screws or anterior variable-angle locked plating, whereas other eight pairs with complex fractures were split for either TBW through two parallel cannulated screws plus circumferential cerclage wiring, or anterior variable-angle locked plating using a cortical caudo-cranial polar screw. Each specimen was tested over 5000 cycles with a range of motion from 90° flexion to full extension by pulling on the quadriceps tendon. Interfragmentary movements were captured by motion tracking.

RESULTS

For both fracture types, the longitudinal and shear articular displacements, measured between the proximal and distal fragments at the central patella aspect between 1000 and 5000 cycles, together with the relative rotations of these fragments around the mediolateral axis were all significantly smaller following anterior variable-angle locked plating versus TBW, p ≤ 0.01.

CONCLUSIONS

From a biomechanical perspective, anterior locked plating of both simple and complex patella fractures resulted in less interfragmentary displacement under extended cyclic loading.

Separate vertical wiring plus bilateral anchor girdle suturing fixation for the fractures of the inferior pole of the patella

BACKGROUND

The fixation of inferior pole fractures of the patella (IPFPs) is still a great challenge for surgeons.

MATERIALS AND METHODS

We introduced a new fixation method for IPFP fixation, that is, separate vertical wiring plus bilateral anchor girdle suturing fixation (SVW-BSAG). Three finite element models including the anterior tension band wiring (ATBW) model, separate vertical wiring (SVW) model and SVW-BSAG model, were built to evaluate the fixation strength of different fixation methods. A total of 41 consecutive patients with IPFP injury were enrolled in this retrospective study, including 23 patients in the ATBW group and 18 patients in the SVW-BSAG group. The operation time, radiation exposure, full weight-bearing time, Bostman score, extension lag versus contralateral healthy leg, Insall-Salvati ratio, and radiograph outcomes were employed to assess and compare the ATBW group and SVW-BSAG group.

RESULTS

The finite element analysis confirmed that the SVW-BSAG fixation method was as reliable as the ATBW fixation method in terms of fixed strength. Through retrospective analysis, we found that there was no significant difference between the SVW-BSAG and ATBW groups in age, sex, BMI, fracture side, fracture type, or follow-up time. There were no significant differences between the two groups in the Insall-Salvati ratio, 6-month Bostman score, and fixation failure. Compared with the ATBW group, the SVW-BSAG group showed advantages in intraoperative radiation exposure, full weight-bearing time, and extension lag versus the contralateral healthy leg.

CONCLUSION

The finite element analysis and clinical results showed that SVW-BSAG fixation methods are a reliable and valuable for IPFP treatment.

Ring-Pins combined with cable cerclage for the fixation of displaced inferior patellar pole fractures

Objective

The study aimed to present the clinical results and complication rates of ring-pins with cable cerclage for treating the inferior pole of patella fracture.

Method

A study that retrospectively reviewed consecutive patients of the displaced inferior pole of patella fracture (AO/OTA 34-A1) operated with a ring-pin tension band using cable cerclage between October 2015 and October 2017 was performed. The duration of surgery, motion range of the knee, function outcomes, and complications were recorded.

Results

The average follow-up of 31 patients was 21 months. The mean operation time was 50 min. Fractures in all 31 patients healed at a mean duration of 8 weeks. There was no infection, no withdrawing of ring-pins, no implant breakage, and no loss of fracture reduction. The mean range of motion was 120°, and no patient complained of implant irritation at the final follow-up. The average Bostman score was 29.0 points, and 28 patients graded clinical outcomes excellent and 3 patients graded clinical outcomes good at the last follow-up.

Conclusions

Ring-pin combined with cable cerclage for treating the displaced inferior pole of patellar fracture is simple, and the postoperative internal fixation-related complication rate is low. It is a good choice for treating the displaced inferior pole of the patellar fracture.

Transosseous suture versus suture anchor fixation for inferior pole fractures of the patella in osteoporotic bone: a biomechanical study

BACKGROUND

The surgical treatment of inferior patellar pole fractures can be a challenge, especially in geriatric patients, who are particularly frequently affected by osteoporosis. The objective of this biomechanical study was to compare the performance of suture anchor and transosseous suture fixation in fractures of the inferior patellar pole in context of bone mineral density.

METHODS

Twelve fresh-frozen human cadaveric knees received a transverse osteotomy, simulating an AO/OTA 34C1.3 inferior pole fracture of the patella. These fractures were fixated with either suture anchors (SA; Corkscrew® FT 4.5 mm) or transosseous suture (TS; #2 FiberWire®). Cyclic loading tests were performed by pulling the quadriceps tendon against gravity from 90° flexion to almost full extension (5°) for 1000 cycles. Motion and fracture gap displacement were tracked until failure occurred. Subsequently, loading to failure tests followed. Differences between groups were compared using unpaired t-tests, and correlations were calculated with Pearson's correlation coefficient.

RESULTS

The suture anchor group showed significantly fewer cycles to failure than the transosseous suture group (SA: 539.0 ± 465.6 cycles, TS: 1000 ± 0 cycles, P = 0.04). Bone mineral density correlated positively with cycles to failure in the suture anchor group (Pearson's r = 0.60, P = 0.02). No differences in fracture gap displacement could be proven after 100 cycles (SA: 4.1 ± 2.6 mm, TS: 6.5 ± 2.6 mm, P = 0.19); 500 cycles (SA: 6.4 ± 6.1 mm, TS: 9.6 ± 3.8 mm, P = 0.39); and 1000 cycles (SA: 4.0 ± 0.4 mm, TS: 11.0 ± 4.5 mm, P = 0.08). Furthermore, the mean destructive load to failure in the suture anchor group was also significantly lower than in the transosseous suture group (SA: 422.4 ± 212.2 N, TS: 825.7 ± 189.3 N, P = 0.04).

CONCLUSIONS

Suture anchors may be a viable alternative to transosseous suture in younger patients for clinical advantages, but in osteoporotic bone, the more stable osteosynthesis with transosseous suture continues to prove superior. Therefore, trauma surgeons might consider the use of transosseous suture in elderly patients, especially in those presenting with low bone mineral density values.

Efficacy comparison of Kirschner-wire tension band combined with patellar cerclage and anchor-loop plate in treatment of inferior patellar pole fracture

Objective: This study aimed to compare the biomechanical stability and clinical efficacy of the Kirschner-wire (K-wire) tension band combined with patellar cerclage and an anchor-loop plate (ALP) in treating inferior-pole patellar fracture.

Methods: The finite element model was established to analyze the mechanical properties of a K-wire tension band combined with patellar cerclage and ALP fixation in the treatment of inferior patellar pole fracture. The clinical data of 49 patients with patellar inferior-pole fracture (AO/OTA 34 A1) admitted to our hospital from January 2017 to July 2021 were retrospectively analyzed. Among these, 28 cases were fixed with ALPs (ALP group) and 21 cases were fixed with K-wire tension bands combined with patellar cerclage (K-wire group). By reviewing the medical records and follow-up results, we compared the operation time, final knee joint activity, incidence of secondary surgery, postoperative complications, and joint function recovery between the two groups.

Results: The biomechanical analysis of the finite element model showed that the maximum displacement of the K-wire group was 1.87 times that of the ALP group. The maximum stress of the K-wire group was 1.34 times that of the ALP group. The maximum stress of the pole bone in the K-wire group was 13.89 times that of the ALP group. The average follow-up times of the K-wire group and ALP group were similar (p > 0.05), and the average ages of the two groups were similar (p > 0.05). The operation time of the ALP group was significantly shorter than that of the K-wire group (p < 0.05).The final knee joint activity of the ALP group was significantly greater than that of the K-wire group (p < 0.05). The Bostman patellar fracture function score of the ALP group was significantly better than that of the K-wire group at 3 and 9 months after operation (p < 0.05). Postoperative complications of the two groups included 1 case (3.6%) in the ALP group with internal fixation-stimulation complications and, in the K-wire group, 3 cases (14.3%) with internal fixation stimulation complications and 1 case (4.8%) with infection.

Conclusion: The ALP and K-wire tension band combined with patella cerclage models were tested at 500 N, and no damage occurred, indicating that the newly designed ALP is safe in mechanical structure. The ALP has better therapeutic effect in biomechanical stability, postoperative complications, secondary surgery, and knee function. This technique is an effective method for the treatment of inferior-pole patellar fracture.

A Novel Technique for the Treatment of Inferior Pole Fractures of the Patella: A Preliminary Report

Objective

Most inferior pole fractures of the patella are comminuted. Therefore, an ideal treatment method has not been determined. We have presented a modified tension band fixation technique—the Krachow suturing, Nice knot combined with tension band fixation—and reported the results of the procedure.

Methods

A total of 16 inferior patellar pole fractures were treated at our institution between January 2019 and October 2020, 15 of which underwent treatment with the modified tension band fixation technique consisting of Krachow suturing with Nice knots combined with tension band fixation. The primary measures: knee motion, Bostman score, anterior knee pain, fixation failure.

Results

Bone union occurred at a mean of 9 weeks postoperatively (range: 8–13). There were no cases of postoperative anterior knee pain, refracture of the inferior patellar pole or wire breakage. The patients regained full ROM of the knee joint without functional deficits during follow‐up; the mean ROM was 128.46° ± 7.07° (range: 113.4°–137.8°). At the last follow‐up, all patients had a mean Bostman score of 28.40 ± 1.29 (range: 26–30), with an excellent score in 11 patients and a good score in four patients.

Conclusion

The modified tension band fixation technique for the treatment of inferior patellar pole fractures is a simple and easy‐to‐perform surgical technique that provides stable fixation and good functional results.

Design and Validation of a Smile-Necklace Plate for Treating Inferior Patellar Pole Avulsion Fractures: A Review and Hypothesis

The patella's inferior pole transmits force generated by contraction of the quadriceps muscle to the tibial tuberosity through the attached patellar ligament, thus completing knee extension. Therefore, fractures of the patella's inferior pole disrupt the coherence of mechanical transmission in the lower extremities. There appears to be no consensus among trauma centers regarding the treatment of infrapatellar pole fractures, primarily because there is no consistent design or application of internal fixation for this type of fracture. We designed a new internal implant similar to the smile necklace based on our previous study. This smile‐necklace plate (SNP) has the advantage of both plate fixation and tension‐band wiring fixation, permitting early rehabilitation, especially in osteoporotic comminuted infrapatellar pole fractures. Finite element analysis helped verify the biomechanical advantages of the SNP in comparison with existing studies. Hence, this novel implant is a promising treatment option for inferior pole patellar fractures.

Treatment of inferior pole fracture of the patella with tension-free external immobilization

Background

Inferior pole fracture of the patella (IPFP) has small and comminuted fracture blocks that are hard to immobilize, and early mobilization may lead to loss of fracture reduction and immobilization failure. Therefore, a difficulty of treatment is to achieve rigid immobilization with early functional exercise. Here, a new treatment method of tension-free external immobilization is put forward.

Methods

The clinical data of 11 IPFP patients treated with tension-free external immobilization from May 2016 to June 2019 were retrospectively analyzed. There were six males and five females aged 39.0 ± 12.8 years (range 18–53 years). IPFP was caused by traffic accidents in five cases and falls in six cases. All cases had unilateral closed injuries, including four in the left knee and seven in the right knee. The preoperative range of motion of the knee was 22.0 ± 7.5° (10–30°). The time from injury to operation was 4.5 ± 1.3 d (3–7 d). The operation-related indices were recorded, and the function of the affected knee was assessed by the Böstman score.

Results

All operations were successful. The operation time was 56.4 ± 8.4 mi (45–70 min), the intraoperative blood loss was 54.1 ± 14.6 mL (40–80 mL), and the length of hospital stay was 7.5 ± 1.9 d (5–11 d). The mean follow-up time was 20.4 ± 7.6 months (12–36 months), the duration of fracture healing was 8.9 ± 1.5 weeks (7–12 weeks), and the removal time of the external immobilization device was 10.4 ± 0.9 weeks (9–12 weeks). At the last follow-up, the range of motion had no significant difference between the affected knee (129.7 ± 3.3°, range 125–135°) and the unaffected knee (130.8 ± 3.8°, range 126–137°) (t = 0.718, p < 0.05). The Böstman score of the knee was 29.2 ± 1.0 points (27–30 points), including 10 excellent cases (90.9%) and one good case (9.1%).

Conclusion

Tension-free external immobilization is a feasible treatment for IPFP. It can help with early functional exercise and achieve a satisfactory clinical effect.

Suture anchor fixation of comminuted inferior pole patella fracture-novel technique: suture bridge anchor fixation technique

PURPOSE

Comminuted inferior pole fractures of the patella are notorious fractures where it is difficult to obtain rigid internal fixation by conventional tension band wiring. The purpose of this study is to evaluate the clinical and radiological outcomes of the suture bridge anchor fixation for these comminuted inferior pole fractures of the patella.

METHODS

From March 2012 to December 2018, suture bridge anchor fixation for the inferior pole comminuted fracture of the patella was performed in 22 patients. There were 21 patients of inferior pole comminuted fracture and 1 patient of lower periosteal sleeve avulsion fracture. Clinical outcomes including SF-36 score, Knee injury and osteoarthritis outcome score (KOOS) and post-operative range of motion were evaluated. In all patients, suture bridge anchor fixation was performed and, tension band wiring with K wire was added for large fragment fixation in two patients. We evaluated bony union, the patellar height using Insall-Salvati ratio and its complications.

RESULTS

Mean age was 46 ± 20 (15-82) years. Mean follow-up period was 25 ± 18 (11-74) months. In all patients, bony union was achieved at postoperative 4 months. At final follow-up, mean SF-36 score was 72 ± 15 (30-91) points and KOOS score was 66.7 ± 16 (43-97). The average range of motion was 134 ± 5 (125-140) degrees. As a complication, one patient developed a wound infection and subsequent osteomyelitis of inferior pole fracture fragment. Compared to the normal knee, the Insall-Salvati ratio of the injured knee averages 0.73 and this smaller ratio less than 0.8 meant patella baja.

CONCLUSIONS

In the comminuted inferior pole fractures of the patella, suture bridge anchor fixation showed good bony union and satisfactory clinical outcomes at the short-term follow-up and could be a satisfactory alternative treatment option. Even though suture bridge anchor fixation in these fractures caused decreased Insall-Salvati ratio (patella height), any patellofemoral pain and limited range of motion was not developed.

LEVEL OF EVIDENCE

Level IV.

Novel Rim Plating Technique for Treatment of the Inferior Pole Fracture of the Patella

To aim of the present paper was to introduce a novel fixation technique for the treatment of inferior pole fracture of the patella. We performed a prospective observational study of consecutive cases of inferior pole fracture of the patella that were treated at our institution between January 2018 and June 2019. The patients include three men and one woman, with an average age of 47 years (range: 42–59 years). All patients were treated with the novel rim plating fixation technique for preserving the inferior pole of the patella. During the surgery, a 2.4 mm straight locking compression plate was contoured to adapt to the arc of the lower half of the patella as the rim plate. After reduction of the fracture, the rim plate was fixed to the proximal fragment of the patella through multiple locking screws, against the continuous pull of the patellar tendon. The rim plate encircles and constricts the inferior pole fragments, functioning as a compression and blocking construct. If necessary, an additional anterior tension band or mini locking plate can be used to further prevent anterior displacement of the inferior pole fragments. Under this rigid fixation, motion of the knee and full weight‐bearing were encouraged postoperatively. The patients were followed up monthly until 12 months after surgery. The time to achieve 90°pain‐free, full range of motion of the knee, and fracture healing, were recorded. Related complications were monitored, including infection, loss of reduction, fixation failure, anterior knee pain, and soft‐tissue irritation. The modified Cincinnati knee rating system was used for knee function assessment. The average operative time was 58.8 min (range: 52–63 min). The average blood loss was 59.8 mL (range: 45–71 mL). For all patients, pain‐free 90° range of motion was restored in 2–4 weeks, and the full range of motion was restored in 8–11 weeks. All patients achieved bone union in 6–9 weeks with no displacement of the fragments or breakage of the implant. No patient complained of anterior knee pain or soft‐tissue irritation. The modified Cincinnati score at 12‐month follow up demonstrated excellent outcomes in all four patients. The rim plating technique may be a feasible option for the treatment of the inferior pole fracture of the patella.

Comparison of a Novel Tension Band and Patellotibial Tubercle Cerclage in the Treatment of Comminuted Fractures of Inferior Pole of the Patella

Objective

To assess the therapeutic effect of a novel tension band using 3.0 mm cannulated screw combined with a titanium cable and specific shims comparatively with patellotibial tubercle cerclage in comminuted fractures of the inferior pole of the patella.

Methods

The retrospective study from March 2012 to July 2017 was conducted in Peking University Third Hospital and comprised 63 patients with comminuted fractures of the inferior pole of the patella: 41 treated with new tension band using 3.0 mm cannulated screw combined with a titanium cable and specific shims (new tension band group) and 22 with patellotibial tubercle cerclage (tubercle cerclage group). Gender, age, AO/OTA fracture type, injury mechanism, inter‐fragmentary gap, and follow‐up time of patients were recorded. Two groups were compared regarding: operation time, blood loss, partial weight‐bearing time, fracture‐healed time, Bostman score and knee mobility at 12‐month follow‐up, and postoperative complications. Continuous and categorical parameters were analyzed by Mann‐Whitney U test and the chi‐squared test, respectively. Fisher's exact test was used for small data subsets.

Results

Between the two groups, no statistically significant difference was found in mean age, gender, AO/OTA fracture type, injury mechanism, mean inter‐fragmentary gap, or mean follow‐up time (P > 0.05). The mean operation time of new tension band group was significantly longer than that of tubercle cerclage group (76.4 min vs 64.2 min, P = 0.006), while there was no significant difference in blood loss. After surgery, new tension band group had a significantly earlier mean partial weight‐bearing time (5.2 weeks vs 7.4 weeks, P < 0.001) and fracture‐healed time (9.6 weeks vs 11.6 weeks, P < 0.001). At 12‐month follow‐up, patients of new tension band group had a significantly higher mean Bostman score (28.5 vs 25.8, P < 0.001) and knee mobility (126.7 vs 117.3, P < 0.001). Ten complications related with internal fixation were found in tubercle cerclage group including two cases of loose internal fixation, two cases of cerclage breakage, and six cases of low patella position who undertook secondary operation. No complications were found in new tension band group (0 in 41 vs 10 in 22, P < 0.001).

Conclusion

Patients with comminuted fractures of the inferior pole of the patella treated with a novel tension band experienced a longer operation time, but earlier partial‐weight‐bearing and fracture‐healed time, better clinical outcomes at 12‐month follow‐up, and less complications. It should be considered an alternative therapy for the treatment of distal pole patellar fractures.

Plating of patella fractures: techniques and outcomes

Operative treatment of displaced patella fractures with tension band fixation remains the gold standard, but is associated with a significant rate of complications and symptomatic implants. Despite the evolution of tension band fixation to include cannulated screws, surprisingly little other development has been made to improve overall patient outcomes. In this article, we present the techniques and outcomes of patella plating for displaced patella fractures and patella nonunions.

Open reduction and internal fixation of displaced patella inferior pole fractures with anterior tension band wiring through cannulated screws

OBJECTIVE

To present the treatment outcome for patients with displaced inferior pole patella fractures treated with anterior tension band wiring through cannulated screws.

DESIGN

Case series.

SETTING

Academic Level I trauma center.

PATIENTS/PARTICIPANTS

During a 2-year period between January 2007 and December 2008, 10 consecutive patients (mean age, 59.8 years) with distal pole fractures of the patella (Orthopaedic Trauma Association 45.A.1) were prospectively enrolled in this study.

INTERVENTION

All 10 patients underwent vertical skin exposure, fracture open reduction, and internal fixation by anterior tension band wiring through 4.0-mm cannulated screws.

MAIN OUTCOME MEASUREMENTS

The range of motion, loss of fracture reduction, implant migration, material failure, soft tissue irritation, and Bostman score and Short Musculoskeletal Functional Assessment dysfunction score were primary outcome measures.

RESULTS

There were three single-fragment fractures and seven comminuted fractures. With 1-year follow-up, all fractures healed clinically in an average of 8 weeks and radiographically on average by 12 weeks. The average range of knee motion arc was 122.5° (range, 95°-140°). Five patients have an average flexion lag of 17° (range, 10°-30°). No patient had loss of fracture reduction, implant migration, material failure, or soft tissue irritation. The average Bostman score was 28.7 out of 30 (range, 27-30), and average Short Musculoskeletal Functional Assessment dysfunction score was 24.1 out of 100 (range, 15-39). All 10 patients stated they were highly satisfied.

CONCLUSION

Anterior tension band wiring through cannulated screws for displaced inferior pole patella fractures is a safe, simple, and reliable alternative treatment with minimal soft tissue irritation. Good functional results and recovery can be expected.