Thomas D. Cahalan

Effect of femoral offset on range of motion and abductor muscle strength after total hip arthroplasty

At a minimum of one year after operation, we studied 64 patients with 86 total hip arthroplasties (THA) by standard anteroposterior hip and pelvic radiographs and measurement of range of motion and of isometric abduction strength. The femoral offset correlated positively with the range of abduction (p = 0.046). Abduction strength correlated positively with both femoral offset (p = 0.0001) and the length of the abductor lever arm (p = 0.005). Using multiple regression, abduction strength correlated with height (p = 0.017), gender (p = 0.0005), range of flexion (p = 0.047) and the abductor lever arm (p = 0.060). Our findings suggest that greater femoral offset after THA allows both an increased range of abduction and greater abductor strength.

Quantitative measurements of hip strength in different age groups

The purpose of this study was to develop a clinically useful method of assessing the strength of the hip musculature and to develop a normal data base with this technique. The strength of 72 subjects aged 20-81 years (37 women and 35 men) was measured through the use of a modified Cybex II with an upright stabilization frame for testing sagittal and frontal plane motions; transverse plane motions of internal and external rotation were tested in the seated position. The subjects were tested at multiple isokinetic speeds and isometric angles. Regardless of age or gender, hip extensors were the strongest muscle group, following by flexors, adductors, abductors, and rotators. As the velocity of exercise increased, the magnitude of the torques produced decreased. Demographically, younger men produced the greatest torques and older women the lowest. The strength values of older men and younger women were similar. The results have clinical implications for objective assessment of strength in pathologic patient populations.

V-Y quadricepsplasty in total knee arthroplasty

The results in 14 consecutive patients (16 knees) who have had total knee arthroplasty (TKA) with a V-Y quadricepsplasty were reviewed. There were eight men and six women with an average age of 66.2 years. Nine patients (ten knees) had revision arthroplasty and five patients (six knees) had primary arthroplasty. Nine of the 14 patients were examined and evaluated in the biomechanics laboratory using the modified Cybex-II system at a mean of three years from surgery. Using the knee rating score of the Hospital for Special Surgery, there were two excellent, ten good, two fair, and two poor results. The average active range of motion was 4 degrees to 85 degrees. Biomechanical testing revealed statistically significant weakness in extension compared with the contralateral side only at test speeds of 120, 180, and 240 degrees per second in those patients who had contralateral normal knees. The affected side at other test speeds were weaker but did not reach statistically significant weakness when compared with the contralateral knee. Comparing V-Y quadricepsplasty to normal medial parapatellar TKA patients, the extensor mechanism was weaker in the V-Y group but not to a significant degree. If one requires a V-Y quadricepsplasty during TKA, one can expect near normal active extension and moderate weakness in extension. Knee scores reflect the difficult reconstructive challenges that are inherent in patients who require a V-Y quadricepsplasty.

Shoulder strength analysis using the Cybex II isokinetic dynamometer.

The purpose of this study was to establish a data base of normal shoulder strength of young adults using the Cybex II dynamometer and specially designed fixation devices. Fifty healthy subjects aged 21 to 40 years old (26 men, 24 women) were tested. The mean peak torque values of their shoulders were measured at speeds of 0 degree, 60 degrees, 180 degrees, and 300 degrees per second. Mean peak torque values generally decreased as speed increased. Men were significantly stronger than women for all motions and speeds tested. Shoulder extension torque was greatest followed by adduction, flexion, internal rotation, abduction, and external rotation. Torque production tended to be greater on the dominant side.

Salvage of Failed First Metatarsophalangeal Joint Implant Arthroplasty by Implant Removal and Synovectomy: Clinical and Biomechanical Evaluation*

Implant removal and synovectomy were used to treat the failure of 14 first metatarsophalangeal joint implant arthroplasties. Revision surgery was performed at an average of 3.1 years after arthroplasty. Follow-up (average 4.9 years) was possible in 10 patients, and clinical results were excellent in seven patients, good in one patient, fair in one patient, and poor in one patient. No significant changes in alignment occurred, although a trend toward toe extension was noted. Dynamic force plate studies in these patients demonstrated less pressure under the first metatarsal head and greater loading under the lateral forefoot. The great toe had less contact time during gait in the involved feet than in the control feet.

Biomechanics of the golf swing in players with pathologic conditions of the forearm, wrist, and hand

Golf is an activity generally stressful to the hands and wrists and particularly can produce increasing symp toms in players with underlying problems such as hand and wrist arthritis or tendinitis. The purpose of this study was to quantitate wrist motion and club head/ ball impact force in subjects with pathologic conditions of the hand, wrist, or forearm, within a laboratory environment. A regular straight-handled golf club was compared to a new BioCurve handle design that has a 19° ulnar bend. We measured and compared the effect of the two grips on wrist motion, club head velocity, ball impact force, ball impact location, and isometric torsional strength in 20 subjects who had a variety of upper extremity disorders. This data was then com pared to data collected in an identical fashion from golfers without such conditions. The results of our study show that there were no differences related to club handle design on impact force or impact location, club head velocity, or club head path and face angle. Wrist kinematic differences were minimal between handle designs. The differences that were significant (P < 0.05) centered around the decreased ulnar deviation of the left hand that resulted when subjects used the BioCurve handle design, which also allowed greater resistance to torque than the straight grip club. In addition to collecting objective data, we asked subjects for their opinions of the two grips. As a whole, the normal group and the group with pathologic conditions noted more comfort, improved grip, and less shock transmission with the BioCurve handle.

The relationship of strength and jump height in figure skaters

Eighteen junior elite figure skaters were filmed while performing axel and double axel jumps. These same skaters were assessed for strength of the shoulders, knees, and hips at multiple angular velocities using a Cybex II system. The height of the jumps was signifi cantly correlated with the strength data. Knee exten sion at 240 deg/sec and shoulder abduction at 300 deg/sec were shown to be the most important strength parameters in determining the height of the jump. This information may be useful for designing strength train ing programs for figure skaters.

Shock-absorbing effect of shoe insert materials commonly used in management of lower extremity disorders

The efficacy of 3 shock-absorbing materials was compared by determining impact characteristics with a drop test method and also by testing the effect of each material when used as a shoe insert in 16 asymptomatic subjects. Peak vertical ground reaction force (F1, F2, F3) and temporal force factors (T1, T2, T3) were obtained with a force plate at a high-frequency sampling rate. Impact force, impact time, impact slope, and impact energy were determined. A standard weight was dropped from 3 heights on each material covering the force plate while reduction of peak force was compared. Impact force was attenuated most effectively by Insert 3 (polymeric foam rubber) and averaged 11% less than that in shoes without inserts. Impact time was increased for all 3 inserts. Impact slope and impact energy were reduced significantly in Insert 3. There was a significant difference in peak vertical force F1 for all 3 inserts, in vertical force F2 for Insert 2 (viscoelastic polymeric material), and in vertical force F3 for Insert 2. Drop-test studies showed that at all ball heights, the highest mean peak force was observed consistently in Insert 2.

Isometric and isokinetic endurance testing of the forearm complex

The purpose of this study was to investigate the rela tionship of isometric and isokinetic endurance of the forearm complex under maximum effort in a healthy population. Isometric and isokinetic endurance meas urements of elbow flexion and extension of the domi nant and nondominant sides were made in 32 healthy male subjects (age range, 21 to 39 years). Both fatigue rates and the amount of time elapsed in reaching fatigue were determined. Analysis of these data reveals that 1) isometric endurance of the forearm complex cannot be used as a predictor of isokinetic endurance, as there is no relationship between the two, 2) dominant and non dominant endurance are related, a result that supports the belief that in the assessment of the endurance of a single diseased upper extremity, the best available comparison is with the contralateral healthy extremity, and 3) healthy males in the age range tested have greater endurance in elbow extension than in flexion.

Kinematics of the Elbow During Wheelchair Propulsion: A Comparison of Two Wheelchairs and Two Stroking Techniques

OBJECTIVE The kinematics of the elbow joint were studied for two types of wheelchairs and during two types of propulsive strokes. PARTICIPANTS Ten serially selected healthy volunteers propelled a standard and a lightweight wheelchair on a roller system with both circular and pumping strokes. DESIGN Kinematic data for the wheelchair and the upper extremity were collected by an optical tracking system. These kinematic descriptors were subsequently time-normalized with a spline algorithm to provide a graphic description of the wheelchair strokes. MAIN OUTCOME MEASURES Thirteen discrete variables were compared for the two chairs and the two propulsive strokes. RESULTS Total elbow motion ranged from 60.9 degrees of flexion to 5.2 degrees of extension. Maximal elbow flexion velocity ranged from 515.4 degrees to 572.8 degrees per second. Kinematic differences between the two wheelchairs were minimal, with a trend for 8.3 degrees to 5.2 degrees more elbow flexion in the lightweight wheelchair (p < .05), depending on the stroke used. With the use of any one chair, the style of the stroke had no significant effect on elbow kinematics, but the use of a pumping stroke did decrease propulsion arc by 12 degrees to 14 degrees (p < .05). CONCLUSION No major differences regarding elbow kinematics were seen between the two types of wheelchairs. The pumping-stroke technique resulted in a shortened handrim contact arc.