This text appeared in issue 2021-04 of the e-mail newsletter orthopädie aktuell of the eurocom e.V., European Manufacturers Federation for Compression Therapy and Orthopaedic Devices.
The Effects of Muscular Imbalance on the Orthopedic Management of Postoperative Unstable Hip Joints After the Repositioning of a Total Endoprostheses (T.E.P.)
A typical complication in the early rehabilitation phase after a T.E.P. is the dislocation of the hip endoprosthesis. Thanks to advanced surgical techniques, the rate of dislocations after primary surgeries has decreased to 1-2%, and after revision surgeries to about 5%. With approx. 210,000 primary implantations and approx. 36,000 revision implantations, there is still a patient population of 3,900 to 6,000 p.a. with a dislocation of the endoprosthesis.
The primary risk factors of a dislocation are not so much to be found in surgical errors, but rather in the patient’s incorrect movements and/or a distinct muscular weakness in the case of an elderly patient. Since elderly patients represent the significantly largest group of patients, the probability of a muscular imbalance existing already before the surgery is high. Due to this, a lower muscular stabilization of the implant can be expected after surgery. This is particularly important regarding movements that promote dislocation, such as standing up from a seat that is too low, which can happen quickly and without noticing in the patient’s everyday life during the aftercare phase or at home, despite appropriate rehabilitative information. This can result in dislocation.
In the past, rigid pelvic casts were used after the successful reduction of the hip joint to prevent dislocation. Later, these were replaced by rigid orthoses. These offered unquestioned protection against reluxation, but did so at the cost of immobilization for a period of up to 12 weeks. This immobilization supported the tendency for atrophy of the mostly already existing muscular imbalances. For a long time, post-surgical treatment after the reduction of a hip joint was not possible without pelvic casts or rigid orthoses due to a lack of alternatives.
In 2004, this situation gave rise to the concept of a partially immobilizing orthosis, which was developed to combine an equally high degree of dislocation prophylaxis with the simultaneous avoidance of immobilization. The core approach for the development of this orthosis was the clinical analysis of the typical movement patterns of a hip T.E.P. patient, and the question of which movement posed which risk of dislocation. The previous approach of achieving dislocation protection by immobilizing all movement patterns was differentiated with regards to the movements that actually required the limiting protection of an orthosis. This allowed a radically new concept for a hip orthosis , which interferes only minimally with the patient’s gait pattern  and at the same time provides effective protection against dislocation in movements that pose a risk of dislocation .
 Heisel J., Thiel C., Neue dynamische Orthese zur Behandlung des postoperativ instabilen Hüftgelenks. Deutscher Ärzteverlag OUP 2015; 4 (2)
 Horstmann T., Rapp W., Innervationscharakteristik der Beinmuskulatur beim Tragen einer Hüftorthese. Persönliche Mitteilung (2008)
 Heisel J., Dynamische Hüftorthese zur Behandlung der postoperativen Instabilität nach Hüft-TEP. Orth. Prax. 2006; 42: 493
1 J. Heisel: Prof. Dr. Dr. hc. mult. J. Heisel, former Head Physician at the Fachkliniken Hohenurach, Bad Urach