Trans-patella tendon approach for domed lateral unicompartmental knee arthroplasty does not increase the risk of patella tendon shortening

Purpose

Shortening of the patella tendon has been noted after total knee arthroplasty and has been associated with diminished functional outcomes. Traumatic and/or ischaemic injury peri-operatively are suggested causes. The Oxford domed lateral unicompartmental knee arthroplasty (UKA) requires a vertical incision through the patella tendon to facilitate orientation of the proximal tibial saw cut; this may induce scarring or impair vascularity of the tendon and can cause shortening. This study investigated the hypothesis that the trans-patella tendon incision increases the incidence of patella tendon shortening after domed lateral UKA when compared to flat lateral UKA performed without the trans-patella tendon incision.

Methods

The radiographs of 50 patients who underwent domed lateral UKA, using the trans-patella tendon approach, and a cohort of 30 patients who underwent flat lateral UKA, in which an incision through the patella tendon was not employed, were reviewed retrospectively. The patella tendon length (PTL) and the Insall–Salvati ratio were measured. In addition, pre-operative and post-operative clinical scores were recorded using both the OKS and AKSS. A change in PTL of greater than or equal to 10 % was considered to be significant.

Results

In the domed lateral UKA group, 13 patients demonstrated a >10 % change in the PTL at 1-year post-surgery (2 shortened and 11 lengthened). In the flat lateral UKA group, nine patients demonstrated a significant change in the PTL at 1-year post-surgery (2 shortened and 7 lengthened).

Conclusion

This study demonstrated that using a trans-patella approach during lateral domed UKA surgery did not significantly increase patella tendon shortening and did not result in reduced clinical outcomes.

Level of evidence

Retrospective, comparative study, Level III.     

Clinical outcomes of medial patellofemoral ligament repair in recurrent (chronic) lateral patella dislocations

Purpose  

The specific aim of this project was to review a homogenous group of patients who had chosen to undergo medial patellofemoral ligament (MPFL) repair to stabilize their patella after repeat (chronic) patellofemoral dislocations and to record the success of this procedure in stabilizing the patella against further lateral dislocations.     

Asymmetrical total knee arthroplasty does not improve patella tracking: a study without patella resurfacing

It is often suggested that patella tracking after total knee arthroplasty (TKA) with an asymmetrical patella groove is more physiological than with a symmetrical patella groove. Therefore, this study tried to address two questions: what is the effect of TKA on patella tracking, and is patella tracking after asymmetrical TKA more physiological than patella tracking after symmetrical TKA? The patellar and tibial kinematics of five cadaveric knee specimens were measured in the intact situation, after the incision and suturing of a zipper, and after placement of a symmetrical TKA and an asymmetrical TKA, respectively. The patellae were not resurfaced. The flexion-extension kinematics were measured with an internal and external tibial moment to determine the envelope of motion (laxity bandwidth) of the tibio-femoral and patello-femoral articulation. The kinematics after TKA showed statistically significant changes in comparison to the intact situation: patellar medio-lateral translation, patellar tilt and tibial rotation were significantly affected. No statistically significant differences in knee kinematics were found between the symmetrical and the asymmetrical TKAs. We conclude that conventional TKA significantly changes physiological patello-femoral kinematics, and TKA with an asymmetrical patella groove does not improve the non-physiological tracking of the patella.     

Allowing one quadrant of patellar lateral translation during medial patellofemoral ligament reconstruction successfully limits maltracking without overconstraining the patella

Purpose

Graft tensioning during medial patellofemoral ligament (MPFL) reconstruction typically allows for lateral patellar translation within the trochlear groove. Computational simulation was performed to relate the allowed patellar translation to patellofemoral kinematics and contact pressures.

Methods

Multibody dynamic simulation models were developed to represent nine knees with patellar instability. Dual limb squatting was simulated representing the pre-operative condition and simulated MPFL reconstruction. The graft was tensioned to allow 10, 5, and 0 mm of patellar lateral translation at 30° of knee flexion. The patellofemoral contact pressure distribution was quantified using discrete element analysis.

Results

For the 5 and 10 mm conditions, patellar lateral shift decreased significantly at 0° and 20°. The 0 mm condition significantly decreased lateral shift for nearly all flexion angles. All graft conditions significantly decreased lateral tilt at 0°, with additional significant decreases for the 5 and 0 mm conditions. The 0 mm condition significantly increased the maximum medial pressure at multiple flexion angles, increasing by 57% at 30°, but did not alter the maximum lateral pressure.

Conclusions

Allowing 5 to 10 mm of patellar lateral translation limits lateral maltracking, thereby decreasing the risk of post-operative recurrent instability. Allowing no patellar translation during graft tensioning reduces maltracking further, but can overconstrain the patella, increasing the pressure applied to medial patellar cartilage already fibrillated or eroded from an instability episode.

     

Effects of lateral retinacular release on the lateral stability of the patella

The objective of this cadaveric study was to evaluate quantitatively the effects of lateral retinacular release on the lateral stability of the patella. A materials testing machine was used to displace the patella of seven cadaveric specimens 10 mm laterally while measuring the required force, with 175 N quadriceps tension. The patella was connected via a ball-bearing patellar mounting 10 mm deep to the anterior surface to allow rotations. Patellar force--displacement behaviour was tested from 0° to 60° knee flexion. At 0°, 10° and 20° flexion the mean force required to displace the patella 10 mm laterally was reduced significantly due to lateral retinacular release, by 16–19%. The average force required to displace the patella was also reduced for larger flexion angles, although this was not statistically significant. These findings suggest that lateral retinacular release may not be appropriate in treatment of patellar lateral instability.     

Effect of tibial tubercle elevation on patellofemoral compressive force in patellofemoral arthrosis

In this study, the effect of tibial tubercle elevation on the patellofemoral compressive force (PFCF) was investigated in patients with patellofemoral arthrosis. Fifteen (11 women and 4 men) patients who had undergone tibial tubercle elevation were included in the study. The average follow-up was 4.5 years. The mean age of the patients was 59 years (range 34–71 years). They were able to maintain a normal pain-free daily life. Maximal isometric quadriceps force (Q) was calculated by equating the moment generated by this force to the moment of the force measured at the ankle by a modified hand dynamometer. PFCF was calculated from the quadriceps and patellar tendon forces. Statistical analyses were then applied to the measured and calculated quantities. The mean quadriceps force in the operated knee decreased by 20%. Likewise, the mean PFCF was found to be reduced by 30% in the operated knees as compared with the asymptomatic contralateral knees. The above differences in Q and PFCF between the operated knee and the asymptomatic knee were statistically significant (P < 0.05). Therefore, the results of this study do not agree with the previously held view that Q and PFCF increase due to the removal of pain after the elevation operation. It is our contention that comparison of the forces measured preoperatively in a painful joint with the forces that can be attained postoperatively in the pain-free joint can lead to errors in biomechanical evaluations.     

Decreased ratios of lateral to medial patellofemoral forces and pressures after lateral retinacular release and gender knees in total knee arthroplasty

Purpose

To demonstrate that lateral to medial patellofemoral force and pressure ratios could be a surrogate marker of retinacular tension and patellar tracking.

Methods

The patellofemoral forces of six knees from three fresh-frozen half-body female cadavers were evaluated with a capacitive sensor under simulated operative conditions in six staged clinical scenarios: native knees, knee arthroplasty without patellar resurfacing, resurfaced knee and patella, resurfaced knee and patella with lateral release, gender-specific knee arthroplasty with patella resurfacing, and gender-specific knee arthroplasty with lateral release. Maximum force and peak pressure were simultaneously recorded during three to four ranges of motion. Average values were compared between lateral and medial patellofemoral compartments as an objective measure of patellar tracking for the different settings.

Results

Significant differences in lateral and medial force and pressure differentials were seen in most scenarios despite clinically normal patellar tracking. Lateral to medial ratios of maximum force and peak pressure significantly increased after TKA (2.9, 2.1) and after patella resurfacing (2.8, 2.6) compared to the native knee (1.6, 1.8). Addition of a lateral release in resurfaced knees decreased the ratio of lateral to medial patellofemoral forces and pressures as did gender knee arthroplasty (1.5 and 1.1, 2 and 1.3, respectively). Pressure and force values most closely resembled the native knee in the resurfaced knee/resurfaced patella with lateral release and in the gender knee arthroplasty scenarios.

Conclusions

Use of lateral to medial patellofemoral force ratios as a surrogate objective marker for patellar tracking was validated in this study by decreasing ratios observed after lateral release in TKA and with gender-specific implants.     

Reconstructing the anterolateral ligament does not decrease rotational knee laxity in ACL-reconstructed knees

Purpose

Little is known about the anterolateral ligament’s (ALL) influence on knee laxity. The purpose of this study was to investigate rotational knee laxity against a pure axial rotational stress using radiostereometric analysis (RSA) after cutting and reconstructing both the anterior cruciate ligament (ACL) and the ALL.

Methods

Eight human donor legs were positioned and stereoradiographically recorded at 0°, 30° and 60° of knee flexion using a motorised fixture, while an internally rotating force of 4 Nm was applied to the foot. Anterior–posterior and rotational laxity were investigated for knees with intact ligaments and compared with those observed after successive ACL and ALL resection and reconstruction.

Results

After cutting the ALL in ACL-deficient knees, the internal rotation was increased in all three knee flexion angles, 0° (p?=?0.04), 30° (p?=?0.03) and 60° (p?<?0.01) by 1.0°, 1.6° and 2.5°, respectively. However, no decrease in laxity was found after reconstructing the ALL in ACL-reconstructed knees.

Conclusions

The ALL was confirmed as a stabiliser of internal rotation in ACL-deficient knees. However, reconstructing the ALL using a gracilis autograft tendon did not decrease the internal rotation laxity in the ACL-reconstructed knee. Based on the results of this study, we do not recommend reconstructing the ALL in ACL-reconstructed knees to decrease internal knee laxity.

     

The effect of bracing on patella alignment and patellofemoral joint contact area

PURPOSE: To examine the influence of two patellofemoral braces on pain response, patellar alignment, and patellofemoral joint contact area in persons with patellofemoral pain. METHODS: Fifteen women between the ages of 18 and 45 yr with a diagnosis of patellofemoral pain participated. After the assessment of pain response using a visual analog scale, subjects underwent axial plane magnetic resonance imaging of patellofemoral joint at 0 degrees, 20 degrees, 40 degrees, and 60 degrees of knee flexion. Imaging was done with the knee extensors contracted (25% body weight) under three conditions: 1) no brace, 2) On-Track brace, and 3) Patellar Tracking Orthosis (PTO). Measures of mediolateral patellar displacement and tilt and medial and lateral facet contact area were obtained from the magnetic resonance images. RESULTS: On average, the On-Track brace reduced symptoms by 50%, whereas the PTO reduced pain by 44%. When averaged across all knee flexion angles, the PTO and the On-Track brace significantly increased total patellofemoral joint contact area by 52.0 mm (21%) and 59.3 mm (24%), respectively, when compared with the no-brace condition. Bracing had no influence on lateral patellar tilt; however, small but significant changes in lateral patellar displacement were observed. CONCLUSION: Large changes in pain and contact area occurred without sizable changes in patellar alignment. The results of this study suggest that changes in patellar alignment by itself may not be responsible for pain alleviation after patellar bracing.     

急性髌骨外侧脱位患者性别、年龄、解剖参数与髌股关节软骨损伤的相关性

目的 探讨急性髌骨外侧脱位(lateral patellar dislocation,LPD)患者性别、年龄、髌股关节解剖参数与髌股关节软骨损伤的相关性.方法 回顾性分析2015-01至2021-07在武警山东总队医院就诊的115例经临床证实为急性LPD患者的MRI资料,对患者性别、年龄[分为青少年(<18岁)、成人(...     

Exercise for fitness does not decrease the muscular inactivity time during normal daily life

The time spent in sedentary behaviors has been shown to be independent of exercise in epidemiological studies. We examined within an individual whether exercise alters the time of muscular inactivity within his/her normal daily life. Quadriceps and hamstring muscle electromyographic activities and heart rate were measured during 1 to 6 days of normal daily living of ordinary people. Of 84 volunteers measured, 27 (15 men, 12 women, 40.7 years ± 16.5 years) fulfilled the criteria of having at least 1 day with and 1 day without exercise for fitness (total of 87 days analyzed, 13.0 h ± 2.5 h/day). Reported exercises varied from Nordic walking to strength training and ball games lasting 30 min–150 min (mean 83 min ± 30 min). Exercise increased the time spent at moderate‐to‐vigorous muscle activity (6% ± 4% to 9% ± 6%, P < 0.01) and energy expenditure (13% ± 22%, P < 0.05). Muscular inactivity, defined individually below that measured during standing, comprised 72% ± 12% of day without and 68% ± 13% of day with exercise (not significant). Duration of exercise correlated positively to the increase in moderate‐to‐vigorous muscle activity time (r = 0.312, P < 0.05) but not with inactivity time. In conclusion, exercise for fitness, regardless of its duration, does not decrease the inactivity time during normal daily life. This is possible by slight modifications in daily nonexercise activities.     

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.     

Arthroscopic surgery and the lateral release for patellofemoral disorders

A 30° arthroscope, when placed from a portal 4 cm proximal to and in line with the medial edge of the patella,approaches the trochlea at a 30° angle, providing a straight-on view of the patellofemoral joint without distortion. By routinely placing the arthroscope through this portal, patellar tracking can be evaluated and patellar malalignment documented and corrected under direct vision. When a lateral release is performed, the scope is in the proximal superomedial portal and the electrosurgical unit is through the anterolateral portal without the tourniquet being inflated. If subluxation remains after lateral release is performed, the degree of medial imbrication to be done is judged arthroscopically to prevent undercorrecting or over-correcting the patellar realignment. When oblique anteromedialization osteotomy of the tibial tubercle is done, the arthroscopic view assists in determining the degree of medialization of the tubercle to be performed. The maximum medialization is believed to be one half the width of the tubercle and fixed with AO small fragment cancellous compression screws. A lateral release is always performed with this procedure and, if it fails to provide patellar realignment, medial imbrication is added. Postoperative positioning in flexion assists the recovery.     

Strength training does not affect the accuracy of force gradation in an isometric force task in young men

The aim of this study is to investigate potential differences in fine motor control between strength trained (ST) and non-strength trained (NT) individuals. By use of an isometric force production task, two groups, 20 ST (mean age 25.6, SD 4.9) and 19 NT (mean age 24.1, SD 2.9) male individuals, were measured on the ability to control forces with the muscles of their index finger. The maximum voluntary contraction (MVC) was higher in ST than in NT group. Error and SD of the signal increased with increasing force levels in both groups. Despite higher absolute force levels of the ST group, SD and Error were the same in both groups for a given MVC percentage. Signal to noise ratio values showed inverted U-shapes for both groups, with no significant differences between groups on various force levels. The power spectral density analysis disclosed significant differences between groups, with more power in the lowest frequency band (1 - 6 Hz) for the ST group. It is concluded that strength training of arm muscles has no negative effect on the stability of sustained contractions of finger muscles. No evidence was found to support the notion of a loss in accuracy as a result of strength training.     

Aperture fixation instead of transverse tunnels at the patella for medial patellofemoral ligament reconstruction

Purpose  

Medial patellofemoral ligament (MPFL) reconstruction is an effective option for the treatment of recurrent patellar instability. Most techniques utilize the passage of a tendon graft through tunnels at the patella with the risk of patellar fracture. The purpose of this study was to investigate the strength of the recent MPFL reconstruction techniques (transverse tunnel, interference screw, anchor, and docking technique).     

Duration of stretch does not influence the degree of force loss following static stretching

AIM: There is an emerging body of knowledge indicating static stretching (SS) acutely and adversely affects muscle performance. The practical value of this research is limited considering the lengthy stretch durations under investigation. It is unclear if stretch durations typical of those used pre-exercise similarly affect muscle performance. The purpose of this study was to determine if SS using more representative stretch durations affects muscle performance and to establish if changes in muscle performance were influenced by the duration of stretch. METHODS: Following 2 familiarization sessions, 16 recreationally trained males and females participated in 2 randomly ordered experimental sessions. In each session maximal effort hamstring performance was assessed prior to and immediately after 1 of 2 stretching protocols. During one of the protocols participants were required to hold each stretch for 15 s while stretch duration in the second protocol was 30 s. Both protocols consisted of 3 repetitions of 2 stretching exercises. A Kincom isokinetic dynamometer was used to assess hamstring performance during isometric, concentric, and eccentric actions. RESULTS: For each of the three muscle actions a repeated measures ANOVA revealed a significant main effect of time (pre- vs poststretch, P<0.05) but no interaction effect (time x SS protocol). Furthermore, the stretch-induced deficits in muscle performance were consistent across muscle action type. CONCLUSIONS: SS incorporating stretch durations typical of those employed pre-exercise were sufficient to impair muscle performance and the duration of stretch did not influence the degree of force loss. Inclusion of SS, even with short stretch durations, in preparation for strength activities is not appropriate.