Midstance hamstring length is a better indicator for hamstring lengthening procedures than initial contact length.

Children with static encephalopathy often walk with excessive knee and hip flexion throughout the gait cycle. This crouch gait pattern can be debilitating. These children may undergo hamstring-lengthening procedures to correct this crouch gait. Some improve, while others remain in crouch gait or go into knee hyperextension postoperatively, which can ultimately be debilitating. Hamstring muscle-tendon length models are frequently used as indicators when making recommendations for or against hamstring lengthening procedures. According to the literature, most clinicians use the length of the hamstring complex at the initial contact phase of the gait cycle as the primary deciding factor. We hypothesize that the length of this muscle-tendon complex at the midstance phase of the gait cycle is a more stringent criteria for lengthening procedures. A simplified hamstring length model was applied retrospectively to the pre and postoperative three dimensional gait analysis kinematics of 152 subjects to assess preoperative surgical indications and postoperative outcomes. Of the limbs with short hamstrings at initial contact preoperatively, 15% went into knee hyperextension following hamstring lengthening procedures. Cases of hyperextension were even higher (19%) if the hamstrings were also normal to long at midstance. If the hamstrings were short at midstance, only 6 % went into hyperextension. Increasing the criteria to short hamstrings at initial contact and midstance reduced the number of limbs with hyperextension to 0%. It appears that the length of the hamstrings at midstance is an additional predictor of the risk of post-op knee hyperextension from hamstring lengthening procedures, than utilizing the length at initial contact alone. Even though short hamstrings at midstance may be an additional predictor of positive outcomes, it also results in a more conservative approach to surgery by excluding almost half of the patients with short hamstrings at initial contact only, but who may benefit from surgery.

Augsburger S ，White H ，Iwinski H 《-》

Pre-operative hamstring length and velocity do not explain the reduced effectiveness of repeat hamstring lengthening in children with cerebral palsy and crouch gait.

Hamstring lengthening surgery (HSL) is often performed to correct crouch gait in patients with cerebral palsy (CP). However, crouch can recur over time, and repeat HSL may be ineffective. One possible reason is that the hamstrings in repeat HSL patients are neither short nor lengthening slowly and would therefore not benefit from HSL. This study aimed to determine whether the hamstrings are short and/or slow preoperatively only in patients with primary, and not repeat, HSL. We compared pre- and postoperative dynamic semimembranosus muscle-tendon lengths for children with CP who had primary (N = 15) or repeat (N = 8) HSL to a group of control participants (N = 10). Outcome measures were compared between visits (pre- vs. postoperative) and groups (control, primary HSL, repeat HSL) using mixed model analysis. Preoperatively, hamstrings were shorter and slower than normal on average in both HSL groups (p < 0.001); all but 3 limbs (primary 26/28, repeat 13/14) had hamstrings that were shorter and/or slower than controls by more than two standard deviations. Postoperative improvements were observed in the primary HSL group for popliteal angle, initial contact knee flexion, minimum stance knee flexion, and dynamic hamstring length (p ≤ 0.001). The repeat HSL group improved only in dynamic hamstring length (p = 0.004) and worsened in passive knee extension (p = 0.01) and minimum hip flexion in stance (p = 0.04). Hamstrings in both surgical groups on average remained shorter and slower than controls postoperatively (p ≤ 0.001). The fact that repeat HSL is less effective in improving knee motion is not due to a lack of short or slow hamstrings preoperatively. However, in recurrent crouch, short or slow hamstrings do not usually indicate hamstring dysfunction, and correction of other deformities such as rotational malalignment, fixed knee flexion contractures, patella alta, weak calf muscles, and/or loose heelcords should be considered rather than repeat HSL.

Osborne M ，Mueske NM ，Rethlefsen SA ，Kay RM ，Wren TAL ... -  《-》

Percutaneous Hamstring Lengthening Surgery is as Effective as Open Lengthening in Children With Cerebral Palsy.

Nazareth A ，Rethlefsen S ，Sousa TC ，Mueske NM ，Wren TAL ，Kay RM ... -  《-》

Surgical outcomes after single event multilevel surgery in cerebral palsy patients with mid-stance knee hyperextension.

Some patients with cerebral palsy (CP) exhibit excessive knee flexion at initial contact followed by knee hyperextension (KE) in mid-stance. This study investigated the change in sagittal kinematics after distal hamstring lengthening (DHL) and triceps surae lengthening procedures in CP patients with KE, and compared it to those without KE. In addition, the risk factors for the worsening of postoperative KE were analyzed. Consecutive 312 patients (596 limbs) with CP who underwent DHL and triceps surae lengthening were included. All patients underwent preoperative and 1-year postoperative three-dimensional gait analysis. Patients' limbs were divided into the KE and knee flexion (KF) groups, according to preoperative minimum knee flexion in stance. KE was defined as minimum knee flexion in stance less than 0°. The KE and KF groups included 130 and 466 limbs, respectively. Knee and ankle sagittal kinematics significantly improved after surgery in both groups. Minimum knee flexion in stance significantly increased from -6.6˚ to 0.5˚ in the KE group, but decreased from 14.6˚ to 7.8˚ in the KF group. Among the KE group, minimum knee flexion in stance improved in 103 limbs (79.2 %), but worsened in 27 limbs (20.8 %). Degree of preoperative KE was the only factor significantly associated with postoperative worsening of KE (p=0.002). The cutoff value for the worsening of KE was -5.8˚ of preoperative minimum knee flexion in stance. This study demonstrated that the sagittal kinematics of the knee and ankle joints improved after DHL and triceps surae lengthening procedures in CP patients with and without KE. Preoperative degree of KE was a risk factor for the worsening of KE after surgery. Therefore, careful selection for indication of DHL is required to prevent postoperative KE due to overlengthening of the hamstrings, particularly in patients with severe preoperative KE.

Chung CY ，Kwon SS ，Park MS ，Lee KM ，Sung KH ... -  《-》

Ankle and knee coupling in patients with spastic diplegia: effects of gastrocnemius-soleus lengthening.

Baddar A ，Granata K ，Damiano DL ，Carmines DV ，Blanco JS ，Abel MF ... -  《JOURNAL OF BONE AND JOINT SURGERY-AMERICAN VOLUME》