Medial patellar ossification after patellar instability: a radiographic finding indicative of prior patella subluxation/dislocation

Objective  To describe the correlation between medial patellar ossification and prior patella subluxation and/or dislocation. Materials and methods  A retrospective billing database search identified 544 patients who had been diagnosed with patellar instability over a 13-year period. One hundred twenty-eight patients met the inclusion criteria. After review by a staff orthopedic surgeon and two musculoskeletal radiologists, 28 patients were found to have medial patellar ossification. The size and location of medial patellar ossification was recorded. Results  Of the 28 patients (20 males, eight females, age 13–66 years, mean 28 years) who were found to have medial patellar ossification, 22 had radiographs, 16 had magnetic resonance imaging, and ten had both. The medial patellar ossification ranged in size from 2 to 18 mm with an average of 6.8 mm. Twelve were located in the medial patellofemoral ligament (MPFL), 14 in the medial joint capsule, and two in both the MPFL and joint capsule. Twenty-seven of 28 patients had a single ossification, and one patient had two ossifications. The timing from injury to first imaging of the lesion ranged from 10 days to a chronic history (≥35 years) of patellar instability. Conclusion  Medial patellar ossification correlates with a history of prior patella subluxation and/or dislocation. The medial ossification can be seen within the MPFL or the medial joint capsule, suggesting remote injury to these structures. The presence of this lesion will prompt physicians to evaluate for patellar instability.     

Diagnosis and treatment of patients with patellofemoral pain

The patient-athlete with patellofemoral pain requires precise physical examination based on a thorough history. The nature of injury and specific physical findings, including detailed examination of the retinacular structure around the patella, will most accurately pinpoint the specific source of anterior knee pain or instability. Radiographs should include a standard 30 degrees to 45 degrees axial view of the patellae and a precise lateral radiograph. Nonoperative treatment is effective in most patients. Prone quadriceps muscle stretches, balanced strengthening, proprioceptive training, hip external rotator strengthening, patellar taping, orthotic devices, and effective bracing will help most patients avoid surgery. When surgery becomes necessary, indications must be specific. Lateral release is appropriate for patella tilt (abnormal rotation). Painful scar or retinaculum, neuromas, and pathologic plicae may require resection. Proximal patellar realignment may be accomplished using arthroscopic or a combined arthroscopic/mini-open approach. Symptomatic articular lesions and more profound malalignments may require medial or anteromedial tibial tubercle transfer. Clinicians should be particularly alert for symptoms of medial subluxation in postoperative patients and should use the provocative medial subluxation test followed by lateral displacement patellar bracing to confirm a diagnosis of medial patellar subluxation. This problem may be corrected in most patients using a lateral patellar tenodesis. Current thinking emphasizes precise diagnosis, rehabilitation involving the entire kinetic chain, restoration of patella homeostasis, minimal surgical intervention, and precise indications for more definitive corrective surgery.     

MPFL reconstruction for recurrent patella dislocation: a new surgical technique and review of the literature

Recurrent dislocation, subluxation and functional instability due to patellofemoral pain might be present in 30 % to 60 % of patients managed non-operatively for posttraumatic patella instability. Disruption of the capsule, medial patella retinaculum and/or vastus medialis obliquus have been associated with recurrent patella instability but recently the medial patellofemoral ligament (MPFL) has been recognised as the most important ligamentous stabiliser preventing lateral dislocation of the patella. Many nonanatomical surgical techniques for the treatment of recurrent patellar dislocation have been described in the literature. These procedures alter the pre-morbid patella mechanics by several principles, including the release of tight lateral ligaments, tensioning of loose medial structures and distal realignment of the extensor mechanism or a combination of these. Very few address the principle site of pathology in patella dislocation, i.e., the torn MPFL. The outcomes are inconsistent and many studies have reported recurrent dislocations and patellofemoral pain and arthritis in up to 40 %. We describe a simple technique of MPFL reconstruction using a single hamstring tendon graft which is passed through the medial intermuscular septum at the adductor's magnus insertion and is fixed to the superomedial pole of the patella. A comprehensive review of the existing techniques of MPFL reconstruction using semitendinosus tendon autografts is also provided.     

Recurrent patellar dislocation after medial patellofemoral ligament reconstruction

We report on three cases of recurrent lateral patellar dislocation following a medial patellofemoral ligament (MPFL) reconstruction for patellar instability. In all three cases, an isolated MPFL reconstruction was performed with a double autogenous gracilis graft. The patellar fixation was done through bone tunnels. All three patients presented with a definite moderate to severe traumatic episode resulting in a recurrent patella dislocation and a transverse avulsion fracture at the medial rim of the patella. All three were treated by an open reduction and internal fixation with good results. No complication or recurrent dislocations occurred. We suggest that this complication is caused by the original underlying pathology such as dysplastic trochlea, abnormal TT–TG, patella alta and hyperlaxity, resulting a greater reliance upon the reconstructed MPFL for patellar stability. When subjected to a severe stress, the graft, which is stronger and stiffer than the original MPFL, will cause a fracture through the medial edge of the patella. This weak area results from the previous drill holes, which act as stress risers.     

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.     

Results of arthroscopic medial retinacular release for treatment of medial subluxation of the patella

BACKGROUND: Medial subluxation of the patella is a rare, disabling condition that has iatrogenic and traumatic causation. To date, only open reconstructions have been reported for operative treatment of this condition, but these procedures have a high rate of complications, revisions, and subsequent surgery. This is the first study to present the results of arthroscopic medial retinacular release for treatment of this problem. HYPOTHESIS: Arthroscopic release will alleviate painful medial patellar subluxation. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Nine knees (7 patients) with painful, recurrent medial subluxation of the patella that occurred spontaneously (2 knees) or after a lateral release (5 knees) or an injury (2 knees) were treated with an arthroscopic medial retinacular release. The retinaculum was released 2 cm medial to the superior pole of the patella down to the anteromedial portal. At a mean follow-up of 2.7 years (range, 1-8 years), all knees were evaluated, and the results were graded according to the Merchant and Mercer rating scale. RESULTS: The mean age of the patients was 25 years (range, 15-38 years), and the mean duration of the subluxations before surgery was 28 months (range, 6-48 months). In all 7 patients (9 knees), the medial release relieved their medial subluxation and knee pain, and there were 6 excellent and 3 good results. There were no complications or further realignment surgery needed after this procedure. CONCLUSION: An arthroscopic medial retinacular release will successfully treat painful medial subluxation of the patella.     

The case for advancement and repairof the medial patellofemoral ligament in patients with recurrent patellar instability

In much of the literature about patellar instability, the role of the passive medial patellar stabilizers traditionally has been ignored or afforded only passing comment. But excessive passive lateral patellar mobility must be considered an essential element in the majority of patients with recurrent acute lateral patellar instability. In patients who have sustained patellar dislocation, numerous authors have shown excessive lateral or total mediolateral patellar mobility compared with normal controls. Clinical and laboratory magnetic resonance evidence suggests that the medial retinaculum shows typical patterns of injury in many cases of acute lateral patellar dislocation. Residual laxity of these soft tissue restraints can be sufficient to allow recurrent lateral instability of the patella after the initial dislocation event. Several studies suggest that the medial patellofemoral ligament (MPFL) is the primary passive soft tissue restraint to lateral patellar displacement. These studies have shown promising evidence that repair and/or advancement of the MPFL is capable of restoring normal lateral patellar mobility in cadaver specimens. If the MPFL is repaired effectively in patients who have sustained retinacular injury in the setting of patellar dislocation, then it should reduce the risk of recurrent patellar instability. In this article, the senior author's surgical technique for advancement and repair of the MPFL is presented. Postoperative rehabilitation is also discussed.     

Medial patellofemoral ligament avulsion injury at the patella: classification and clinical outcome

Purpose

To define medial patellofemoral ligament (MPFL) injury characteristics at the patellar attachment and clinical outcome in patients with primary traumatic patellar dislocation and MPFL avulsion injury at the patella.

Methods

Magnetic resonance imaging (MRI) was used to assess patients with primary (first-time) patellar dislocation and MPFL injury at the medial margin of the patella. Fifty-six patients with patellar attachment MPFL injury were enrolled in the study. Thirteen patients underwent surgical fixation of the avulsed MPFL and patellar medial margin osteochondral fracture, and the remaining patellar MPFL injures were treated nonoperatively. Forty-four patients were evaluated clinically at median four (range 1–10) years after patellar dislocation. The follow-up included evaluation of recurrent patellar instability, subjective symptoms, and functional limitations.

Results

Three types of patellar MPFL injuries were found; type P₀ with ligamentous disruption at the patellar attachment, type P₁ with bony avulsion fracture from the medial margin of the patella, and type P₂ with bony avulsion involving articular cartilage from the medial facet of the patella. Of the patellar MPFL avulsion injuries that underwent initial surgical fixation, two patients (2/13) reported an unstable patella at follow-up. Fifty-five per cent (17/31) of patellar MPFL avulsion injuries that were treated nonoperatively had recurrent patellar instability (n.s.). The median Kujala score was 90 for patellar avulsion with surgical fixation and 86 for patellar avulsion without surgical fixation (n.s.).

Conclusion

Patellar attachment MPFL injury showed three different patterns, classified as types P₀, P₁, and P₂. MRI can be used to assess the injury pattern. Patellar MPFL avulsion injuries do not benefit from acute surgical repair compared with nonsurgical treatment. Type P₂ patellar MPFL avulsion includes an osteochondral fracture that may require surgical fixation.

Level of evidence

Prognostic study, Level III.     

关节镜辅助下修复内侧髌股韧带治疗创伤性髌骨不稳

目的:探讨关节镜辅助下内侧髌股韧带(MPFL)修复术在治疗创伤性髌骨脱位中的效果。方法:2000年12月~2004年2月,收治22例创伤性髌骨不稳患者,其中男性7例,女性15例;年龄16~33岁(平均23.7岁);所有患者在第一次脱位时均有外伤史,术前脱位次数3~7次。术中先进行关节镜检查,评估髌骨轨迹和髌股关节的动态匹配关系,确认MPFL损伤部位后进行修复,并于关节镜下监视调整MPFL的张力。髌骨外侧支持带明显紧张者行关节镜下外侧支持带松解。术后经正规康复治疗。随访24~38个月(平均28.6个月),根据Larsen评分评价术后膝关节功能。结果:22例膝关节术后髌股匹配关系均获得重建,随访期内未发生髌骨再脱位。根据Larsen评分,优18例、良4例。结论:修复MPFL对于创伤性髌骨不稳具有良好的疗效,关节镜是保证手术成功的重要辅助手段。     

Patellar shape can be a predisposing factor in patellar instability

Purpose  

Predisposing factors to objective patellar instability include trochlear dysplasia, patella alta, patellar tilt and elevated tibial tuberosity–femoral groove distance. The shape of the patella is classically not considered a predisposing factor. Anomalies of dynamic and static factors, including excessive patellar height, tibial tubercle lateralisation or trochlear dysplasia, may influence the development of the patella.     

Arthroscopic extraarticular reconstruction of the medial patellofemoral ligament with gracilis tendon autograft - surgical technique

The standard approach to reconstruct the medial patellofemoral ligament (MPFL) is by mini-open incision at its patellar insertion and femoral origin. At the medial patella rim, the MPFL insertion may be visualized in most cases by dissection during surgery. On the femur, it is more difficult to localize the MPFL remnants by a mini-open incision due to soft tissue covering the anatomical origin. Therefore, the femoral MPFL origin is usually identified by intraoperative lateral fluoroscopy. However, the insertion and origin of the MPFL at the patella and femur might be directly visualized using an arthroscopic extraarticular approach from the knee joint through a window of the synovial layer. This is especially helpful on the femoral side but also at the patella to find the individual anatomical MPFL footprints. Arthroscopic extraarticular reconstruction may then be performed using one additional medial mid-parapatellar portal. The major advantages of this technique are an individualized anatomical procedure, which is minimal invasive and cosmetically appealing. The aim of this study was to describe the arthroscopic extraarticular approach to the MPFL insertion at the patella and origin at the femur through synovial windows and to explain the procedure of arthroscopic MPFL reconstruction with a gracilis tendon autograft. Level of evidence Expert opinion, surgical technique, Level V.     

Transient lateral patellar dislocation: review of imaging findings, patellofemoral anatomy, and treatment options

Transient patellar dislocation is a common sports-related injury in young adults. Although patients often present to the emergency department with acute knee pain and hemarthrosis, spontaneous reduction frequently occurs, and half of cases are unsuspected clinically. Characteristic magnetic resonance imaging (MRI) findings often lead to the diagnosis. The purpose of this review is to illustrate the MRI findings of lateral patellar dislocation and concomitant injuries, such as kissing contusions of the medial patella and lateral femoral condyle; osteochondral and avulsion fractures; and injuries of the medial patellofemoral ligament/retinacular complex. This article will also briefly review patellofemoral anatomy and passive, active, and static stabilizers. Predisposing factors for patellar instability, including trochlear dysplasia, patella alta, and lateralization of the patella or tibial tuberosity and their relevant measurements will also be highlighted. Treatment options, including surgery, such as medial patellofemoral ligament reconstruction, tibial tuberosity transfer, and trochleoplasty, and their postoperative imaging appearances will also be discussed.     

Quantitative gait analysis in patients with medial patellar instability following lateral retinacular release

Medial patellar instability is a known possible complication following lateral retinacular release. Insufficient passive structures, muscle imbalance and an over-release of the lateral retinaculum with resection of the vastus lateralis tendon have been implied as a major cause of this problem. We report about the findings of quantitative gait analysis consisting of video recordings, three-dimensional motion analysis, dynamic electromyography and sampling of the ground reaction forces in two patients with medial patellar subluxation. Documentation of the gait functions together with observation of the patellar translation revealed the timing of the occurrence of the instability during level gait: a normal gait pattern with a sufficient quadriceps mechanism and a centred patella was seen during loading (weight acceptance), while the quadriceps muscle was active. Abnormal medial translation of the patella was observed during unloading of the leg while the knee was bending in preparation for the swing phase. This is a phase in the gait cycle when the quadriceps muscle is silent and the patella position is guided by the passive structures only. This finding weakens the argument of muscle imbalance as a cause for the patellar instability and stresses the importance of well balanced passive structures. This explains why a muscular rehabilitation programme is likely to fail as long as the passive structures allow the instability to occur.     

Anatomical double-bundle MPFL reconstruction with an aperture fixation

Since biomechanical studies have shown that the medial patellofemoral ligament (MPFL) is the main restraint against lateral patella displacement, reconstruction of the MPFL has become an accepted method of restoring patellofemoral stability and numerous techniques were described. Due to biomechanical examinations and clinical results, an anatomical double-bundle reconstruction of the “sail-like” MPFL is a reasonable method for achieving stability during complete extension and lower flexion degree. This method also serves to avoid rotation of the patella, providing immediate stability throughout the normal range of motion. However, until today, an aperture fixation technique at the patellar insertion with two bundles has not been described previously. This technique can provide an immediate stability to allow an early rehabilitation with full range of motion.     

The effect of reconstruction of the medial patellofemoral ligament on patellar tracking

We evaluated patellar tracking in six cadaveric knees with the medial restraints intact and then sectioned to determine their contribution to lateral translation of the patella with and without a lateral force on the patella. The medial patellofemoral ligament was then reconstructed with a gracilis tendon graft and patellar tracking was again evaluated. The knees were extended using a materials testing machine, and patellar tracking was measured with a position sensing system. With no lateral force applied to the patella, patellar tracking was unaffected by the presence or absence of the medial restraints or by reconstruction of the medial patellofemoral ligament. With a lateral force applied to the patella, patellar tracking was changed significantly by the loss of the medial restraints. Normal patellar tracking was substantially restored by reconstruction of the medial patellofemoral ligament.     

A mini-invasive adductor magnus tendon transfer technique for medial patellofemoral ligament reconstruction: a technical note

Patellar dislocations are associated with injuries to the medial patellofemoral ligament (MPFL). Several techniques for MPFL reconstruction have been recently published with some disadvantages involved, including large skin incisions and donor site morbidity. Arthroscopic stabilizing techniques carry the potential of inadequate restoration of MPFL function. We present a minimally invasive technique for MPFL reconstruction using adductor magnus tendon autograft. This technique is easily performed, safe, and provides a stabilizing effect equal to current MPFL reconstructions. Skin incision of only 3–4 cm is located at the level of the proximal half of the patella. After identifying the distal insertion of the adductor magnus tendon, a tendon harvester is introduced to harvest the medial two-thirds of the tendon, while the distal insertion is left intact. The adductor magnus tendon is cut at 12–14 cm from its distal insertion and transferred into the patellar medial margin. Two suture anchors are inserted through the same incision at the superomedial aspect of the patella in the anatomic MPFL origin. The graft is tightened at 30° knee flexion. Aftercare includes 4 weeks of brace treatment with restricted range of motion.     

Patellar tracking abnormalities: clinical experience with kinematic MR imaging in 130 patients

A kinematic magnetic resonance (MR) imaging technique for assessment of malalignment of the patella, involving the acquisition of multiple sequential axial images of the patellofemoral joint during the early increments of passive knee flexion, was used to evaluate 130 patients (235 symptomatic patellofemoral joints) showing clinical evidence of having patellar tracking abnormalities. Twenty-three of the patellofemoral joints had undergone previous surgical procedures for patellar realignment. In addition, 14 (28 patellofemoral joints) asymptomatic control subjects were studied. Normal patellar tracking was observed in all of the asymptomatic subjects and in 43 (17%) of the 260 patellofemoral joints in the patient population, 18 (7%) of which were symptomatic. Sixty-nine (26%) of the patellofemoral joints had lateral subluxation of the patella, 106 (41%) had medial subluxation of the patella, 21 (8%) had excessive lateral pressure syndrome, 19 (7%) had lateral-to-medial subluxation of the patella, and two (1%) had dislocation of the patella. Of the 235 patellofemoral joints with suspected abnormalities, 217 (93%) had patellar malalignment. Of the 23 patellofemoral joints that had undergone prior surgery, 20 (87%) had abnormal patellar tracking. Thirteen of 14 (93%) patellofemoral joints that had undergone a prior arthroscopic lateral retinacular release had a medially displaced patella.     

In vitro measurement of patellar kinematics following reconstruction of the medial patellofemoral ligament

This study compares the effects of two different techniques of medial patellofemoral ligament (MPFL) reconstruction, and proximal soft tissue realignment on patellar stabilization against lateral dislocation. Eight human cadaver knee specimens with no radiological pathomorpholgy on a straight lateral view, contributing to patellofemoral instability, were mounted in a kinematic knee simulator and isokinetic extension was simulated. Patellar kinematics were measured with an ultrasound positioning system (zebris^®) while a 100 N laterally directed force was applied to the patella. The kinematics were compared with intact knee conditions under MPFL deficient conditions, as well as following dynamic reconstruction of the MPFL using a distal transfer of the semitendinosus tendon, following static reconstruction by a semitendinosus autograft, and following proximal soft tissue realignment of the patella (Insall procedure). Dynamic reconstruction of the MPFL resulted in no significant alteration (P = 0.16) of patellar kinematics. Static reconstruction of the MPFL significantly medialized (P < 0.01) the patellar movement without, but restored intact knee kinematics under the laterally directed force. In contrast, following proximal soft tissue realignment, the patellar movement was constantly medialized and internally tilted (P = 0.04). Dynamic and static reconstruction of the MPFL create sufficient stabilization of the patella. Following proximal soft tissue realignment, the patellar position was over-medialized relative to intact knee conditions, which could lead to an overuse of the medial retropatellar cartilage.     

Modified Elmslie-Trillat procedure for instability of the patella

The purpose of this study was to determine whether or not the modified medial transfer of the ligamentum patellae in case of objective instability of the patella is an adequate therapy and if it is possible to improve the patellar congruence angle by this method. Between October 1987 and April 1993, 41 operations were performed in 37 patients with medialization of the medial third of the ligamentum patellae with the corresponding part of the tibial tubercule. Four patients needed a bilateral operation; the two interventions were not performed at the same time. Thirty-six operated knees (88%) were examined at a median clinical and radiological follow-up of 62.8 months (± 15.8 SD). For evaluation, the objective and subjective Turba score was used, and pre- and postoperative X-rays were compared. The patients’ average age at the time of intervention was 23.2 years (± 7 years SD). The operation was performed 39 times for recurrent dislocation or subluxation, for patella alta with cartilage tissue damage, and for first time traumatic dislocation. The only postoperative complication was a temporary peroneal paresis. There were no redislocations seen at the follow-up. One patient with repeated subluxations underwent an additional lateral release combined with a repair of the medial retinaculum. In all other cases, the Turba score showed good or excellent results (subjective 1.9; objective 0.8), the patellar congruence angle was significantly improved (P < 0.001), and there were no medial subluxations. We conclude that the transfer of the medial third of the ligamentum patellae for objective instability of the patella is a minimally invasive and adequate technique to improve significantly a pathological patellar congruence angle.     

关节镜辅助下LARS人工韧带重建内侧髌股韧带治疗复发性髌骨脱位

目的探讨关节镜辅助下韧带先进加强系统(ligament advanced reinforcement system,LARS)人工韧带重建内侧髌股韧带(medial patellofemoral ligament,MPFL)治疗复发性髌骨脱位(recurrent dislocation ofpatella,RDP)的临床疗效。方法我院自2007年3月～2008年7月收治了6例RDP(1例为双膝)的患者,术前行X片、CT、MRI了解髌股关节及MPFL情况,术中先用关节镜观察髌股关节的对合关系、运动轨迹及关节软骨情况;用LARS人工韧带重建MPFL;重建后关节镜检查髌股关节对合关系和运动轨迹恢复情况。术后逐步进行膝关节功能锻炼,并用Insall评定标准进行术后评分。结果随访6～24个月,平均13个月,无伤口感染、移植物排斥反应和断裂。按Insall评定标准,优5例,良1例。X片示髌骨复位良好,髌骨无复发性脱位或半脱位。结论关节镜辅助下LARS人工韧带重建MPFL能有效治疗RDP。