Longitudinal Changes in Lower Extremity Alignment and Mechanical Axis Parameters After Bariatric Surgery in Patients With Morbid Obesity: A Prospective Observational Study

NCT07794566 | Active Not Recruiting DMC

• 1 other identifier: MarmaraUSpine02
• Study Type: observational
• Target: 30
• Locations: 1 country
• Sites: 1

Brief Summary

The goal of this prospective observational study is to understand whether major weight loss after bariatric surgery is associated with changes in the alignment of the lower limbs in adults with morbid obesity. The hips, knees, and ankles form a connected weight-bearing system that supports the body during standing and walking. The position of these joints in relation to one another affects how body weight and mechanical forces are transmitted through the legs. In people with severe obesity, increased body weight and changes in body shape may influence the way these forces are distributed across the lower extremities. Bariatric surgery can result in substantial weight loss. However, it is not yet fully understood whether this degree of weight reduction is accompanied by measurable changes in the alignment of the hips, knees, and ankles or in the mechanical axis of the lower limbs. This study will follow patients undergoing bariatric surgery and will evaluate them before surgery and again at approximately 3, 6, and 12 months after surgery. The study is observational. This means that researchers will observe and measure changes that occur during the patients' clinical course rather than assigning participants to a particular treatment for research purposes. The main question is whether lower-extremity alignment and mechanical-axis measurements change during the first year after bariatric surgery as patients lose weight. "Lower-extremity alignment" describes how the hip, knee, and ankle are positioned in relation to one another. The "mechanical axis" is an imaginary weight-bearing line used in orthopedics to describe how forces are transmitted through the leg from the hip toward the ankle. The position of this line in relation to the knee helps doctors understand how weight and mechanical forces are distributed across the lower limb. Researchers will examine radiographic measurements that describe the overall relationship between the hip, knee, and ankle and the contribution of the thigh bone and shin bone to lower-limb alignment. Measurements obtained before bariatric surgery will be compared with those obtained at approximately 3, 6, and 12 months after surgery. Following the same patients over several time points is important because weight loss after bariatric surgery occurs progressively rather than at a single moment. Repeated measurements will allow researchers to determine whether lower-limb alignment remains stable, changes early after surgery, changes gradually as weight decreases, or shows different patterns between individual patients. The study will also explore whether the amount and course of postoperative weight loss are related to any observed changes in lower-extremity alignment. The researchers do not assume that losing weight will automatically correct an existing bow-legged or knock-kneed appearance, or that every patient will show a measurable change in skeletal alignment. Some aspects of lower-limb alignment are determined by the shape and orientation of the bones and may remain stable. Other aspects of weight-bearing posture and the relationship between the joints may potentially change as body weight and body composition change. The purpose of this study is to objectively measure these changes rather than assume that they will occur. Understanding the relationship between severe obesity, substantial weight loss, and lower-extremity alignment may be clinically important because mechanical loading is closely related to the function and health of the hip, knee, and ankle joints. Changes in lower-limb biomechanics may also be relevant to future research examining joint symptoms, osteoarthritis, walking mechanics, and orthopedic treatment planning. The results of this study may therefore improve understanding of how the weight-bearing system of the lower limbs responds to major weight loss after bariatric surgery and may provide a scientific basis for further studies focusing on obesity and musculoskeletal health. For patients and families, the study can be summarized simply as follows: the researchers want to find out whether losing a substantial amount of weight after bariatric surgery changes the way the legs line up from the hips through the knees to the ankles. Measurements obtained before surgery will be compared with measurements obtained at 3, 6, and 12 months after surgery. By observing the same patients throughout the first postoperative year, the researchers hope to understand whether weight loss changes the mechanical alignment of the lower limbs and, if changes occur, when they become measurable.

Conditions

Obese; Limb Deformities; Arthritis

Keywords

Bariatric Surgery; Weight Loss; Lower Extremity Alignment; Mechanical Axis; Hip-Knee-Ankle Alignment; Coronal Alignment; Knee Alignment; Lower Limb Biomechanics

Outcome Measures

Primary Outcomes (1)

• Change From Baseline in Hip-Knee-Ankle (HKA) Angle

  The Hip-Knee-Ankle (HKA) angle will be measured in degrees on standing full-length lower-extremity radiographs using the mechanical axes defined by the centers of the femoral head, knee, and ankle. An HKA angle of 0° represents neutral mechanical alignment. Changes in HKA angle from the preoperative baseline will be evaluated at each postoperative follow-up to determine longitudinal changes in coronal lower-extremity alignment.

  Baseline (preoperative), and 3, 6, and 12 months after bariatric surgery

Secondary Outcomes (4)

• Change From Baseline in Mechanical Axis Deviation (MAD)

  Baseline (preoperative), and 3, 6, and 12 months after bariatric surgery

• Change From Baseline in Mechanical Lateral Distal Femoral Angle (mLDFA)

  Baseline (preoperative), and 3, 6, and 12 months after bariatric surgery

• Change From Baseline in Medial Proximal Tibial Angle (MPTA)

  Baseline (preoperative), and 3, 6, and 12 months after bariatric surgery

• Change From Baseline in Joint Line Convergence Angle (JLCA)

  Baseline (preoperative), and 3, 6, and 12 months after bariatric surgery

Study Arms (1)

Patients Undergoing Bariatric Surgery

Adults with morbid obesity undergoing bariatric surgery as part of routine clinical care will be prospectively followed. Lower-extremity coronal alignment, hip-knee-ankle relationship, mechanical axis, and related radiographic alignment parameters will be evaluated before surgery and at approximately 3, 6, and 12 months after surgery to assess longitudinal changes associated with postoperative weight loss.

Other: Obese.

Interventions

Obese. OTHER

Participants will undergo bariatric surgery as part of routine clinical care according to established clinical indications. The type of bariatric procedure will not be assigned or modified by the study. Participants will be prospectively followed, and lower-extremity alignment and mechanical-axis parameters will be evaluated using standing full-length lower-extremity radiographs before surgery and at approximately 3, 6, and 12 months after surgery. The study will assess longitudinal changes in hip-knee-ankle alignment and related femoral, tibial, and knee joint-line parameters during postoperative weight loss.

Patients Undergoing Bariatric Surgery

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)
• Sampling Method: Non-Probability Sample

Study Population

Adults with morbid obesity undergoing bariatric surgery as part of routine clinical care will be prospectively enrolled and followed. Lower-extremity coronal alignment and mechanical-axis parameters will be evaluated using standardized standing full-length lower-extremity radiographs obtained before surgery and at approximately 3, 6, and 12 months after surgery. Serial measurements will be used to evaluate longitudinal changes in hip-knee-ankle alignment and related femoral, tibial, and knee joint-line parameters during postoperative weight loss.

You may qualify if:

• Adults aged 18 years or older.
• Patients with morbid obesity who are scheduled to undergo bariatric surgery according to routine clinical indications.
• Ability to stand independently for standardized weight-bearing lower-extremity radiographic assessment.
• Availability of an appropriate preoperative standing full-length lower-extremity radiograph allowing assessment of the hip, knee, and ankle centers.
• Planned postoperative clinical and radiographic follow-up at approximately 3, 6, and 12 months.
• Ability and willingness to participate in the prospective follow-up protocol.

You may not qualify if:

• Previous lower-extremity corrective osteotomy, joint arthroplasty, or major reconstructive surgery that substantially alters mechanical alignment.
• Previous fracture malunion or major skeletal deformity involving the pelvis, femur, tibia, knee, or ankle that prevents representative mechanical-axis assessment.
• Neurological or neuromuscular disorders substantially affecting standing lower-extremity alignment.
• Inability to obtain technically adequate standardized standing full-length lower-extremity radiographs.
• Pregnancy at a time when radiographic assessment would otherwise be required.
• Major lower-extremity trauma or surgery occurring during follow-up that may independently alter mechanical alignment.
• Incomplete or unavailable radiographic data required for longitudinal analysis.

Sponsors & Collaborators

• Marmara University: lead

Study Sites (1)

Department of Orthopaedic Surgery and Traumatology, Marmara University, Pendik Training and Research Hospital, İstanbul, Turkey

Istanbul, Pendik, 34899, Turkey (Türkiye)

Location

Related Publications (1)

• Does extreme weight loss after bariatric surgery alter spinopelvic parameters and ameliorate back pain? A retrospective case study Fırat Emin Özdemir1, Hakan Şeşen1, İsmail Demirkale3, Doğan Öztürk2, Hakan Buluş2, Murat Altay1 1Department of Orthopedics and Traumatology, University of Health Sciences, Atatürk Sanatoryum Training and Research Hospital, Affiliated by Gülhane School of Medicine, Ankara, Türkiye 2Department of General Surgery, University of Health Sciences, Atatürk Sanatoryum Training and Research Hospital, Affiliated by Gülhane School of Medicine, Ankara, Türkiye 3Department of Orthopedics and Traumatology, University of Health Sciences, Prof. Dr. Cemil Taşcıoğlu City Hospital, Affiliated by Hamidiye School of Medicine, Istanbul, Türkiye

  BACKGROUND

MeSH Terms

Conditions

Obesity; Arthritis; Weight Loss

Interventions

Adiposity

Condition Hierarchy (Ancestors)

Overweight; Overnutrition; Nutrition Disorders; Nutritional and Metabolic Diseases; Body Weight; Signs and Symptoms; Pathological Conditions, Signs and Symptoms; Joint Diseases; Musculoskeletal Diseases; Body Weight Changes

Intervention Hierarchy (Ancestors)

Body Fat Distribution; Body Weights and Measures; Body Constitution; Physical Examination; Diagnostic Techniques and Procedures; Diagnosis; Body Composition; Biochemical Phenomena; Chemical Phenomena; Metabolism; Physiological Phenomena

Study Officials

• Muhammed F Serttaş, Medical Specialist, Consultant

  Department of Orthopaedic Surgery and Traumatology, Marmara University, Pendik Training and Research Hospital, İstanbul, Turkey

  PRINCIPAL INVESTIGATOR

Study Design

• Study Type: observational
• Observational Model: COHORT
• Time Perspective: PROSPECTIVE
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: August 23, 2026
• First Posted: August 31, 2026
• Study Start: September 7, 2026
• Primary Completion (Estimated): August 1, 2027
• Study Completion (Estimated): August 1, 2027
• Last Updated: September 16, 2026

Record last verified: 2026-08

Data Sharing

• IPD Sharing: Will not share

Locations

TU (1)